Generators

In this unit we constructed a wind turbine. You may have seen these generators placed on the countryside somewhere. They are generators and utilize mechanical energy in order to produce electrical energy. The wind pushes fan blades which turns either a loop of wire around magnets or magnets around a loop of wire. The wire feels a force from the magnets and creates an electrical charge. This is known as magnetic induction. In order to build a wind turbine it is important to understand different designs. There are three general designs for wind turbines that exists today. One design is know as Savonius VAWT. This is the design my group decided to use. This design caches the wind effectively and is able to spin freely.

For this project you will need:

Screw  1

Washer ($.18 x 2)

¼ x 2/2 wood ($.97 x 2)

dower ($.98 max price)

Smart water bottle ($1.50 x 2)

Grand total: $6.28

Expected Materials:

Hot glue (a lot)

Hot glue gun

Drill

Saw

Copper wire (a lot)

My group then went to Lowes in order to purchase the required materials. We purchased four washers, one wood round rod, two pieces of wood (¼ x 2/2 wood ($.97 x 2)) and two smart water bottles. The water bottles would be cut and used as the fan blades. We decided to use smart water bottles since the plastic is light and capable of holding a large force. These blades were glued onto the round wooden rod which was sharpened one side. The sharpened side of the rod would then be laced on the screw which was screwed into your base. When the sharpened stick was placed on the top of the screw it was able to move fast. The base would resemble a box. The top to the base would have a hole which would keep the wind turbine from falling down. This base allowed the wind turbine to stay in position and  move when the wind was added. 

Now the important part about making the turbine is coiling the copper wire correctly. For the copper wire my group decided to make 4 sections of 200 coils of wire. In order to coil the wire it is necessary to leave a small piece of wire free. This allows you to attach the coils to the voltmeter when testing the wind turbine. It is important that all the coils of wire are in the same direction. If the wires are not in the same direction than no electricity will be produced. Once one section of wire is coiled, leave a little space free and then coil the second wire 200 coil wraps. This is preformed 4 times. An easy method is to use a circular object to wrap the copper wire around. Once all the wire has been wrapped in the same direction cut the wire leaving a little space to attach the end into the volt meter. It is important to remove the plastic coating on each end of the wires. This need to be done or else the volt meter will not register any voltage. We placed the copper wire around the screw in order to be closer to the magnets. If the copper wire is close to the magnets than it will feel a greater force. This in turn will produces a greater voltage .

  

My group ended up having two series of fan blades. We attached three fan blades on the top half of our wooden rod and three smaller fan blades on the bottom of the rod. We also attached a small cardboard circle on the bottom of the wooden rod. This small cardboard circle contains the magnets. We used the washers as a means of attaching the magnets without using super glue. The magnets were placed on the washers which were glued onto the cardboard. When the fan blades caught the wind, the rod moved in a circle and thus moved the magnets around the coils of wire. These coils of wire generated electricity. Our design produced 0.121 volts. Not enough to power a small light bulb but still produced electricity. My advice to other attempting to create a wind turbine is to use a larger amount of copper wire and use more magnets. A different design can be used to catch the wind better It makes a large difference if the plastic coating on the copper wire is complete scrapped off.

Top 10 Places to Find Physics

There are many places where physics is found in our everyday lives. Many of these situations are unnoticed and therefore unappreciated. Physics surrounds our lives, if you like it or not its everywhere. In this post I will discuss the top 10 most frequent places where physics is present and you may not be aware of it!

10. Generator:
As you are reading this, you are using a computer. Your computer has a transformer in it which utilizes two different coils of wire. One coil of wire is used to either reduce or increase the voltage that enters into your computer. A generator is also used to power the computer. This generator (the power company) inputs mechanical energy in order to either a) turn a coil of wire around a magnet or b) turn a magnet around a coil of wire. This coil of wire feels a force from the magnet and thus generates electricity. This energy is then sold to you in order to power your electronic appliances such as the computer.

9. Motor:
Our automobiles, blenders.. anything that transforms electrical energy into mechanical energy is influenced by physics. A motor works when a current carrying wire feels a force from a magnet. The magnet thus causes the copper wire to torque and either spin he blades in a blender or the wheels in a car.

8. Tides:
You may not be aware of tides but if you live on the coast (such as myself) it influences your life. The tides are controlled by the position of the moon. The moon causes a gravitational force between the earth since it has a substantial mass and is located close to the earth. This gravitational force causes high tides and low ides in our world. These tides can produce a substantial amount of electricity when harnessed.

7. Balance:
Tight-rope walkers utilize balance in order to walk across the rope. We balance our selves when we carry a back pack or a handbag without even noticing it. Balance is when our center of gravity is underneath our base of support. When this is not present, the object will fall. A tight-rope walker will often carry a long pole across the rope in order to lower their center of gravity, closer to the rope.

6.  Air resistance:
Air resistance is all around us and is usually negligible when calculating physics equations. If you want to go sky diving, this is a very importance force to have acting against you. Air resistance will increase as your speed increases when you are falling through the air. Eventually, the force of air resistance will be equal and opposite to the force of gravity and therefore you will have a constant velocity. If air resistance was not equal and opposite, you would accelerate to the point in which stopping would be impossible.

5. Gravity:
Gravity is probably the most influential force that effects our every day lives. It affects our weight since it is the force in which the earth pulls us to the ground. If you went to the moon your weight would be significantly different however your mass would remain the same. Without gravity, we would not be able to walk and if we jumped, we would continue to increase height forever. A hover craft makes friction negligible and allows the craft to continue with a constant velocity indefinably.

4. G. Force:
Newtons first law states that an object in motion will stay in motion unless acted on by a non-zero net force. When a car accelerates, we sink back into the seat because our body wishes to stay at rest but is forced to move forward. When in an airplane, g-forces can be experienced. This occurs when acceleration is felt as weight. When an airplane pitches up, you will sink back into your seat and feel heavier and thus experience a g-force.

3. Airbags
Airbags are installed in every car as a safety precaution. They deploy during accidents in order to protect the inhabitants of the vehicle. When an airbag deploys we go from moving to not moving. The change in moment is the same whether we hit the dashboard or the airbag. If the change in momentum is the same, than Impulse is also the same. Whether you hi the airbag or the dashboard since impulse is the same, airbags will increase the time and the force therefore decreases. This decrease n force protects us from a large blow.

2. Stop Lights:
Stop lights are everywhere and not many people really understand how they operate  A stop light receives a signal when a car moves over wires embedded in the ground. Since the car has magnets, the wire feels a force from the magnet and produces electricity. This signal is then sent and translated to the presence of a vehicle. Now you know why stop lights change from red to green!

1.  How does a horse pull a buggy or How do we move forward:
This is a difficult concept to understand but it occurs every day. A horse pulls a buggy because the horse exerts a force equal and opposite to the force that the buggy exerts. This is because newtons third la states that every action has an equal and opposite reaction. The buggy moves forward because the horse exerts a greater force on the ground than that of the buggy.

Unit 7 Blog Reflection

For this unit, my physics class discussed magnets and electromagnetic induction. We will be discussing magnetism (magnetic poles; electromagnets), forces on charged particles in an electric field (motors), electromagnetic induction, generators, and transformers.

Guiding Question- Why does a paperclip stick to a magnet?

Magnetism is surrounded by the common knowledge that all charges are magnetic and moving charges causes magnetism. Each electron is spinning in a domain. A domain is a cluster of electrons spinning in a random direction. When an object is magnetized all the domains line up in the same direction . All of the electrons run towards the north pole and run away from the south pole. These electrons eventually go through the north pole and come back around to the south pole. The movement of electrons are represented as lines and referred to as field line. The north pole of a magnet sticks to the south pol of another magnet because the field lines math up. The north pole of a magnet repels the north pole of another magnet because the field lines are opposite. If a magnet is cut in half, you you have a north side and a south side? The answer is no! You will just have two magnets now! Talk about saving you money. When referring to the paper clip question, it is important to realize that the paperclip has no set poles. The domains in the paperclip are random. A domain is a cluster of electrons that are spinning in the same direction. The magnet has a magnetic field. when the magnet is close to the paperclip the domains of the paperclip align to match the magnetic filed of the magnet. The paperclip now has a north and south pole. The north pole of the paperclip is attracted to the south pole of the magnet and thus the clip will stick to the magnet! We also discussed the northern lights and why they occur. The northern lights are caused by comic rays entering our atmosphere. Why do we only see these rays at the poles? The rays are noticed at the poles because when the magnetic field is parallel to a charged particle, the charged particle will not feel a force. When a particle is perpendicular to the magnetic field, it will feel a force and therefore bounce off. The rays feel a fore at the equator since the charged particle is parallel to the magnetic field of the earth. The northern lights enter at the poles because they are parallel to the magnetic field. This causes an increase in cancer at the poles since these rays contain cosmic radiation.

Guiding Question #2:  What is needed to construct a motor?

Know we know that a charged particle feels a force form a magnetic field when it is perpendicular. This causes the particle to 'bounce off' and feel a force. We can apply this idea to a motor. A motor is used to transfer electrical energy, into mechanical energy. A motor is constructed from a battery, a rubber band, two paperclips, a coil of copper wire, and a magnet. The copper wire is made into a loop with two strands sticking out from either side. The copper wire is mounted over the magnet which is placed on the battery. The paper clips position the copper wire over the magnet and complete the circuit. The rubber band is used to hold the motor together. The main idea behind a motor is that a current carrying wire feels a force from the magnet. the magnet exerts a force on the copper wire since they are perpendicular. This causes the copper wire to torque. We could attach fan blades to make a fan or even wheels to make a car. The spinning wire, produces mechanical energy, capable of moving and object.

Guiding Question #3: How does a credit card work?

A credit card, traffic light, metal detector all work utilizing the ideology of electromagnetic induction. The basic idea surrounding this is a loop of wire in a complete circuit with no current has a magnet moved through or over the wire. This magnetic filed charges the wire and endues a current. The current can be used for a variety of things, If the magnet is constantly moved, changing the charge, a generator is created. A credit card contain a series of magnets in the black strip. There is a coil of wire in the credit card machine. As the credit card is moved through the machine, the magnets change the magnetic field within the loop of wire. This change in magnetic field endues a charge which is translated by the machine. The machine translates this signal into you credit card number. This answer an be adapted to answer how a traffic light detects a car, or how a metal detector detects metal. Pretty cool but we are not done yet!!

Guiding Question #4: What is the difference between a motor and a generator?

A generator has the same concept as the credit card machine in the previous question. A generator produces electricity by putting mechanical energy in. This is entirely different from a motor which transfers electrical energy into mechanical energy. The generator has a coil of wire and a magnet  The magnet is either moved around the coil of wire or the coil of wire is moved around the magnet. A generator requires an ac current. The current need to be alternating or else the coil of wire will not feel a force. generators are used to power our homes during a power out. Normally the mechanical energy is either steam or wind, but can also be physical turning or fuel could be used.

Guiding Question #5: What is so special about transformers?

A transformer is used either increase the amount of voltage or decrease the amount of voltage in an appliance, Your computer has a small black or white box attached to the power cable. This transformer is used to convert the 120V in the wall into 300V in the appliance (these are made-up numbers). This increase in voltage is referred to as a step-up and commonly occurs for big appliances such as the washing machine or a microwave. A step-down transfer occurs when the energy is produced from the power company and transferred to your house. The power company makes the current very low and the voltage very high. This is done to reduce unnecessary power loss. if the current is very high, the power lines will heat up. Once the energy has reached your house it under goes a step-down. This occurs because in the transformer are two sets of wires. If we step down then the primary coils inside the transformer are larger than the secondary. If you want less voltage, then there will be less coils. We can calculate the number of coils in the primary or secondary or calculate the voltage in the primary or secondary. We use the formula;
                   Primary # of Coils/ Primary Voltage = Secondary # of Coils/ Secondary Voltage

For this unit, I found the motor section difficult to understand. During class we were explained that 'a current carrying wire feels a force from the magnet which causes it to torque.' I was always confused on what the force was that produced this torque but never fully understood. This topic, although appears difficult, needs to be taught in a specific order. I really enjoyed building the motor since it allowed me to have a visual and better understand the importance of every part. I hope that you build a motor!!

Motor Blog

In class today, we learned how to build motor. Motors are used in our every day lives and it is therefore important to understand what it is. A simple motor consist of a battery, copper wire and a magnet. In class today we were given a rubber band, two paper clips, a long strand of copper wire, a battery and a magnet. The goal of this lab was to make the copper wire spin. This is accomplished by constructing a motor. The two paper clips are placed at each side of the battery and suspend the loop of copper wire over the magnet. The paper clips create a circuit that is closed when the copper wire is added. The magnet is placed below the copper wire, on top of the battery. When building this motor it is important to suspend the copper wire just over the magnet, not touching. When a current is sent through the copper wire, the magnetic field produced by the magnet, causes a force on the moving electrons. This is similar to cosmic rays trying to enter the earths atmosphere. The cosmic rays bounce off the earths atmosphere because it is perpendicular to the earth magnetic field. The electrons in the copper wire and deflected by the magnetic field since they are perpendicular  If the copper wire was parallel, it would not feel a force from the magnet. The magnet causes the copper wire to spin as long as there is a current running through the wire. It is vital to scrap the ends o the copper wire in a specific way. We scrap the copper wire to allow electrons to flow and to make the copper wire spin in a certain way. only one side of the copper wire is scrapped. Imagine the wire suspended over the magnet by the paperclips. The current goes through one side of the copper wire and is forced by the magnet to spin. If electrons went through the entire copper wire, it would spin back and forth since it would experience two equal and opposite forces.

A motor works because the moving electrons in the copper wire, experience a force from the magnet's magnetic field. This occurs because the copper wire is perpendicular to the magnetic field. The paper clips are used to suspend the wire and to complete the current from the battery to the wire. The rubber band is used to hold these two paperclips in place. motors are used in our everyday lives. It is used in our cars, in fans, in lawnmowers, practically anything. You can attach a fan blade on the end of the wire and create a fan. Its that simple!!

Magnets & Magnetism

Everyone loves Bill Nye and his explanations. In this video we are introduced to magnetism. The video explains that opposite forces attract and like forces repel. The video also explains what would happen to a magnet if it was cut in half. This is a very important concept that is normally overlooked by many individuals. I also found this video helpful since it gave real life examples of magnets in our world. The video does not explain magnetic fields and what they look like which is a very important concept to understand when learning about magnetism. This video does however, explain what magnets are made out of and that our planet is a giant magnet due to the spinning core.

http://www.youtube.com/watch?v=ak8Bh9Zka50

Electricity Unit 6

In this unit my class learned all about electricity. Everyone knows what electricity is but I had no idea why lighting occurs, how a fuse box works and how to make a balloon stick to a wall b rubbing it against your hair. I was exposed to many different phenomenons that occur in a our day to day lives but never really know how they work.

During this unit I learned how a battery, wires, and a light bulb fit together to make a light bulb work. A light bulb has an inert gas inside the glass. Also inside the light bulb is a filament  This filament is usually tungsten and is the part the electricity flows through. In order to light up the bulb with a battery and wires it is important to realize that the circuit needs to be closed. If there is any open space in the circuit then the electricity will not be able to flow. This is why a light bulb doesn't light up if the filament is broken. This means that the circuit is incomplete and the electricity is unable to travel through the system. In a circuit, a light bulb is referred to as a resistor since it uses electricity. Any appliance that is drawing energy is referred to as a resistor. If you jumped off the ground when you touch an electric fence will you get shocked? The answer is no, but don't try it! The electric fence will not shock you because the circuit is not complete, in order for you to feel a shock  you must be touching the ground. The reason you shouldn't try it is because when you get on the ground again and don't let go in time you will feel a shock. If you place a large enough insulator, such as styrofoam under your feet, you will not feel a shock. This occurs because the electricity does not go through the styrofoam therefore the circuit is not complete.

After this introduction into electricity we began learning abut charges. A neutral charge means that there is no overall charge. If something is negatively charged then there are more electrons present. If something is positively charged then more protons are present. We already know that like charges repeal and opposite charges attract (electrons attract protons but repel other electrons). Charges ten to move through contact, friction (two objects rubbing), and induction (a charge is made without contact). An example of friction occurring in our every day lives is when we wear socks and rub the carpet. This friction creates a negative charge in your socks so when you touch someone else and complete a circuit the energy travels through them and they will experience a shock. Induction is a little more complicated. Picture two metal balls both neutral and both touching one another. If you put a negatively charged stick towards one metal ball, the electrons in the rod will repel the electrons in the metal ball. Once the two balls are separated  one will be positively charged and the other will be negativity charged. Lightning is also an example of induction but on a larger scale. The molecules in a storm cloud create a negative charge in the cloud. This charge attracts all the protons on the ground until a path is created between the ground and the lightning. Although the electrons in the cloud is traveling to the ground, the immense energy produces light which is what we see as lightning. Interestingly more, lighting actually goes from the ground up, it just moves too fast for us to notice!

We also learned about polarization during this unit. Conductors allows charges to move through an objects and insulators stop charges from moving. Such materials such as rubber and styrofoam are insulators and metals are normally conductors. An object becomes polar when the charges are separated  The object is still neutral however the charges are separate. Why does ceran-wrap cling on to a bowl? When ceran-wrap is removed from the box the wrap becomes negatively charged due to the friction. When the wrap is placed on the bowl it becomes polar. The negatively charged wrap is attracted to the strong bond between the protons in the bowl. This makes the wrap stick to the bowl. Now, Why does ceran-wrap stick to the bowl when the other charges are repelling the negatively charged wrap? Columbs law states the force between any two objects is inversely proportional to the distance squared.
                                                            Columbs Law: K(q1)(q2)/d^2
The wrap sticks to the bowl because the distance is small between the two negatively charged bowl and wrap making the force small.
To answer this question we have 4 step to follow:
1 step: Plastic wrap is charged by friction and when brought near the bowl, it becomes polarized.
2 step: The positive charges in the bowl move close to the negative plastic wrap and the negative charges in the bowl move away from the wrap.
3 step: The distance between the opposite attractive charges is smaller than the distance between the like repelling charges.
4 step: Since there is a greater distance between the repulsive forces  the force between them will be less than the closer attractive forces. Thus the wrap sticks to the bowl.

Why are electronic devices always put in metal containers?
Many people, such as myself  don't understand this question until it is explained. In order to understand and answer this question we need to know about electric fields. An electric field is an area around a charge that can influence another charge. If a positively charged circuit board is placed in a metal container, all the surrounding charges will become equal and opposite and will therefore not influence the hard drive. It doesn't matter where this positively charged circuit is placed in the container, all the surrounding charges will have no influence with the charge and therefore the hard drive is protected. This is known as electric shielding  Another example of electric shielding occurs when lighting strikes a car. The individuals in the car will be safe in the car.

Voltage is the potential difference between two points. We calculate voltage by dividing electric potential energy by the charge.
                                                                    V= PE/q

During this unit we also learned about Ohm's law. This law states that current is equal to voltage divided by resistance. Current is the ability for electricity to travel through a wire. This is measured in amps and the universal symbol is I. Voltage is the potential difference between two points. Voltage is measure in volts and the universal symbol is v. Resistance is the tendency for a circuit to resist an electrical current and is measured in ohms. We can increase the current through an object by either replacing the material, making the  path wider or longer. Why does a light get dimmer? It is important to remember when answering this question that resistance doesn't change. If we have a 60W light bulb  and it starts to get dimmer, the voltage is decreasing. Which light bulb offers more resistance, a 60W bulb or 120W? this question is a little tricky. The answer is the 60W bulb. The 60W bulb has a shorter, and thinner filament therefore increasing the resistance.

When talking about circuit there are two that we use. One circuit is called a series and another is called parallel. Think of a circuit as a roadway system. A series circuit means that there are multiple red lights on one road. These red lights cause the traffic flow to move slower. In a series circuit, the more appliances are added, the less current is available. This is due to the increase in resistance. In a series circuit if one appliance is removed, the circuit is open and therefore all the appliances turn off. A parallel circuit can closely resemble a rod with multiple routes. If one appliance is removed, the others continue to stay on. A parallel circuit also increases the current since there are more ways for the electricity to travel. Our homes are wired in a parallel circuit. If too many appliances are connected into a parallel circuit then he current becomes too high and can heat up the wire. This was one of the main causes for house fires in the past. We installed a fuse box which contains many circuit breakers. A circuit breaker will trip if too much current is present and will break the circuit. This turns off all the power in the house since a box is wired in a series circuit. We use a series circuit in fuse boxes to protect our homes from house fires!

Fuse Box Photo

      This photo is of a fuse box. A fuse box is put in every home as a safety precaution. A fuse box is wired in a series which means if one of the circuit breaker trips, all the power will be cut off. A circuit breaker trips when too much current is present. This high current is caused when many appliances are plugged into the wall. The more appliances are plugged in, the greater the current. This increase in current occurs since most homes are wired in a parallel circuit. A fuse box will immediately shut off all electricity in a house when it detects a high current. This protects our house from electrical fires.

Mouse Trap Race Car

Mouse Trap Race Cart Stats

Average Speed of Car: 0.68 m/s

Place: 3rd 

            Where do I begin? For our physics class we were instructed to build a mouse trap race car that would have to travel 5 meters down the hallway. Newton’s first law states that if there is no force present on an object, than that object is either moving with a constant velocity or at rest. This law applies to the mouse trap race car since once a force has been applied to the object it will continue at a constant velocity. Although this is true, we live in an imperfect world where friction and air resistance is present. This means that although the car would be moving at uniform speed, due to outside forces, it will eventually slow down and stop moving. Newton’s second law states that acceleration is proportional to force and inversely proportional to the mass of the object. For the mouse trap race car, you want to have a large force while maintaining a low mass. This will allow you to increase the acceleration of the mouse trap car. Newton’s third law of motion states that every action has an equal and opposite reaction.This means that when the wheels of the cart pushes the ground back, the ground pushes the wheels forwards.

For this project my partner and I set some ambitious goals and attempted to make a different type of race car. We wanted to make a race car using two small wheels in the front and two large vinyl records placed in the back. We initially used one record but realized that it wasn't able to support that cart. After constructing this race cart we realized that one of the records was slightly smaller than the other. This proved to be catastrophic since the cart wasn't able to stand up and roll properly. We wanted to use one vinyl record since we wanted to build a race cart that could travel a large amount of distance. We decided to use a vinyl record since it was a larger wheel. This large wheel would cover more distance per rotation. This is optimum if you are designing a distance car. Smaller wheels are used for a speed car since they rotate faster and cover a smaller amount of distance. Since we used a vinyl record we anticipated to use a large lever arm. The race cart wasn't stable enough causing us to shorten the frame and use cds instead of the vinyl records. This allowed for more support and a stable platform. Since we used one wheel in the back, our cart wasn't stable and would flip. The amount of wheels determines the location of the carts center of gravity. One back wheel makes the car more unstable than others with two back wheels. Your race car requires traction on the back wheels. Many of the cds will spin on the ground due to the large pulling force. Many of my fellow class mates and I put tape or balloons around the cds in order to create traction between the wheels and the ground. This added friction allows the wheels of the cart to not spin out on the ground. It is also necessary to eliminate any unwanted friction in the system. Any spots where the cds are touching the frame will cause friction. This is bad since energy is being transferred into heat and not into the movement of the car. The law of energy of conservation states that energy is neither created nor destroyed only transformed. Friction is transformed energy which creates heat. When the spring is set back the cart contains potential energy that is later transformed into kinetic energy.

After several trials we ended up using a large lever arm in order to make the cart move the required 5 meters. Our cart contained a lever arm around 10 inches. It took our cart 7.35 seconds to complete the track. Our cart had some areas which were creating a large amount of friction and therefore we were losing energy in our system. If I were to redo this project I would focus more on the lever arm and the string system.

           

           When building a race car it is vital to understand a lever arm and how it affects the torque. The lever arm controls the speed of the cart and the distance. With a longer lever arm, torque becomes increased. The mouse trap is the only source of energy located on the cart. The mouse trap allows the cart to move. When you connect a long wire to the mouse trap spring it acts as a lever arm. This lever arm, when combined with a force (the mouse trap spring) creates torque. The larger the lever arm the larger the torque will be since the torque is calculated by multiplying force by the lever arm. This torque is what causes the cart to move forward. The lever arm is attached to a sting which is tied onto the back axle  Once you wind up the string, the mouse trap will move forward which will spin the axle  This causes the mouse trap to mouse the cart forward. It is important that the sting falls off the back axle  This allows the cart to move freely once the mouse trap has been fully extended forward.

            

           Although the mouse trap car has potential and kinetic energy we are unable to calculate these values. We are unable to calculate the amount of work the spring does on the car because work is a parallel force. The weight of the car and the force of the spring are not parallel forces and therefore we are unable to calculate the amount of work done by the car. This also means that there is no change in kinetic energy and therefore there is no potential energy. My initial car design changed drastically since it was an ambitious design. The changes were necessary due to the unstable frame and location of the carts center of gravity. During the car design it was extremely difficult to build the axles  I struggled with the idea of the axles for a large amount of time. Once I constructed the axles the next big problem was securing the lever arm onto the mouse trap. This was difficult since the hot glue couldn't hold the force of the spring. I later wrapped these two parts with copper wire and added a small amount of hot glue. This secured the lever arm to the mouse trap and allowed my car to move 5 meters. My advice to others doing this project it to build a cart that has a small force of resistance. I also advise that you make a solid frame that will hold the cart together. The cart also must have a long lever arm in order to travel long distances. I also advise you to have fun and try something new!

Unit 6 Reflection

In this unit of physics, the class was introduced to energy. We learned about work, power, kinetic energy, potential energy, the law of conservation of energy and mechanics. This unit proved to be more technical as we advanced however the concepts are easy to comprehend. 

Guiding Question: Your force is 200n and you climb 5 meters in 2 seconds. how much work is done? How much power did you generate? 

Work is a force that acts on a body. Work is a parallel force and therefore does not work when the two forces are perpendicular. An example of work is someone walking up the stairs. Since the person has a force of gravity pulling them down, and moving upwards, the person must exert a force to go up the stairs. Since the vector arrows are parallel the person is said to be doing work. An example of someone not doing work is a waiter carrying a tray to a table. Although the waiter is carrying the tray he is not doing any work as he walks to the table. Force and distance must be parallel. If the force applied doesn't cause and object to move, than no work is done. An example of this is someone pushing a wall. Although they are applying a large force, the wall doesn't move and therefore no work is done. Work is measured in joules (a newton-meter). The equation for work is:

                                                        work (Joules) = Force (N) x Distance (meters)

Power, is similar to work, by factors in the amount of time. Power is defined as the rate of work produced. This is measured in watts (joules per second). Power is calculated in the equation below:

                                                         Power (Watts) = Work (joules) / Time (Seconds) 

Knowing this information now, we are able to solve our guiding question;

1. Work = force x distance
2. W = 200 x 5
3. W = 1000J
4. Power = work/time
5. Power = 1000/2
6. Power = 500 watts

In order to climb the stairs it would require 1000 joules  Once at the top you would of produced 500 watt in 2 seconds. 

Guiding Question 2: A ball with a mass of 10kg is dropped off a 200m cliff. What is the velocity of the ball right before it hits the ground

Potential energy is the energy stored in an object based on its mass and height. An object has full potential energy at the top of its path when it is not moving. Once the object begins to move this potential energy becomes transformed into a different form of energy. The energy of motion is refereed to as kinetic energy. The Law of Conservation of Energy states that energy can neither be created nor destroyed, only transformed. As the object falls and gains velocity, it also gains kinetic energy. At the end of the objects path, right before it hits the ground, the object has full kinetic energy. Since the potential energy will eventually be transformed into kinetic energy they are measured in joules. To calculate both potential and kinetic energy, physicists have created two formulas:

                                    Potential energy (Joules) = mass(m) x gravity(g) x height(h)

                                    Kinetic energy (Joules) = (1/2) x mass (m) x velocity^2 (m/s)

With the following information we are now able to answer our second guiding question. 

1. Pe = mgh
2. Pe = (10)(10)(200)
3. Pe = 20000J
4. Pe = Ke
5. 20000 = 1/2(10)v^2
6. the answer is 63.24 m/s.

Guiding Question 3: You need to get a heavy box into your truck. Although you only need to lift the box 2m high, the box has a force of 400n. You have a 3m ramp. How much force would it be to push the 400m box up the 3m ramp?

When we think of a machine we think of electronics (car, computer etc.). A machine also exists in physics. A machine can look like a ramp in the picture above. We can use a simple machines to move heavy object and use less force. The ups man uses a ramp because he is able to use less force by covering a larger distance. To solve for the work done in a simple machine we use the work equation. 

1. Work = mass x distance
2. work = 400 x 2 
3. work = 800J
4. f(3) = 800
5. f = 800/3
6. f = 266.66 N

Now if someone tells you that they have a machine that is 100% efficient, you need to correct them. To calculate the efficiency of a machine we use the equation 

                                                          

                                                             Efficiency = workout/work in 

No machine is 100% effective because we live in an imperfect work. Energy is transformed into friction on a molecular level as well as with air particles. 

Photo of a Ramp

Now you might not be able to see it, but this plane is capable of opening a large section in the middle in order to transport of large materials. When the plane opens up, a ramp is attached since most of the objects are very large. A ramp is known as a simple machine. The ramp is used to bring large objects down and up while only requiring a small force. Since work is parallel, and the ramp is not exactly parallel, a smaller force is required due to the greater distance. Say the ramp is 4 m long and 1m high. The person only has to exert a fourth of the force since he is pushing the object over a larger distance. Although the same amount of work is done, either lifting the box 1 m or pushing the box on a 4m ramp, you exert a smaller force when using the ramp since it has a larger distance.  

Unit 5 Picture

This picture demonstrates a balanced object. The meter stick is placed on the edge of a table with a 100g weight on the end. If you wanted to find the weight of this meter stick you can calculate the torque on one side of the meter stick and then find the force of the meter stick. Torque is the tendency for an object to rotate. Since the meter stick is perfectly balanced we can say that the torque on each side is equal. 

Unit 5 Reflection Blog

During this unit we learned about Rotational motion, Rotational Inertia, Rotational velocity, angular momentum, torque,and centripetal force. This unit was more technical than previous units and proved more difficult to grasp and comprehend. Our introduction to Rotational Motion was difficult to understand. After preforming a demo outside it was easier to understand. We were presented with a question that confused most of the class. If two people are on a merry-go-round, one close to the middle and one far from the middle, who has the greater velocity? Initially, I thought that everyone in the merry-go-round would move at the same speed. During the demonstration the teacher stood in the middle and half the class stood in a line next to the teacher and the other half of the class stood on the other side. We were all told to keep in line with the teacher as we rotate in a circle. Being at the end of the line it proved to be very difficult to keep up with the rotating circle. It then became apparent that although our rotational velocity was the same, we all had a different tangential velocity. Rotational velocity is the amount of rotations in a given time period. Tangential velocity is the rotational velocity of an object over a period of time. The further an object is from the axis of rotation the higher the tangential velocity. When discussing rotational velocity we can use gears. In the picture provided you will notice two gears, one small, and one large. Although they are both rotating with the same velocity the smaller gear is completing one rotation faster than the larger gear. This means that the small gear has a larger rotational velocity than the bigger gear. We apply the idea of gears in many products such as bicycles, and cars.

During this unit we also discussed the implications of putting larger wheels on you car and how it relates to physics. If you put larger wheels on your car without changing the speedometer you may get a ticket. This occurs because the speedometer is programmed to measure rotations per minute and translate it into speed. If you have bigger wheels the speedometer will read a lower speed then when you are actually going. the wheels cover a larger distance in one rotation. With big wheel, one rotation will be a further distance.

Rotational inertia is how much an object is willing to spin. This is the property of an object to resist the change in spin. Rotational inertia depends on where the mass is located. Angular momentum is determined by two factors: rotational inertia  and rotational velocity. Since we know the law of conservation of momentum, we know that the angular momentum before is equal to the angular momentum after. We can control our rotational inertia which directly influences our rotational velocity. An example of this is an ice skater. The ice skater will brim their arms in. close to their axis of rotation to increase there rotational velocity  If the ice skater wishes to slow down they will extend there arms, increasing their rotational inertia and decreasing their rotational velocity.

We also learned torque. Torque is the tendency of an object to rotate around its axis of rotation. The more torque an object has the more likely that object is to rotate. Torque is calculated by multiplying the force applied by the lever arm. An example of torque in the real world is a wrench loosening a bolt. The larger the wrench the larger the lever arm. It is important to remember that torque is a perpendicular force. If an object is balanced it is said to have an equal torque on each side. There is always a counter clockwise torque and a clockwise torque. If the object rotates clockwise, the it has a clockwise torque, if it rotates counter-clockwise, it has a counter clock wise torque. When learning this we were told to predict the mass of a meter stick only using a 100g weight. This demonstration was very difficult since we had to calculate the toque of the meter stick balanced with the 100g weight on it. We then had to determine where the center of gravity for the object is. We learned that the center of gravity for any object is underneath that objects base. This point is where all the mass is also located.

Centripetal force is a center seeking force. Centrifugal force, although not real, is a fleeing force. An example of this force in our everyday life is when a cyclist turns and dosent fall. This occurs because the cyclists support force and force of weight causes him to move towards the center of the circle.

Mass of a Meterstick

During physics class we were instructed to determine the mass of a meter stick by using a meter stick and a weight. In order to fully comprehend the objective of this project it is important to identify where the center of gravity is located. In order to find this point balance the meter-stick without the weight first. For many meter sticks the center of gravity is located close to 50cm. Once you have determined the exact point where the meter-stick can balance you then place the weight on one end of the meter-stick and make it balance balance. For me this point was located at 30cm. We now have to identify that when 100 grams is added to the end of the meter stick, it will balance at 30cm. Torque is the tendency of an object to rotate around the axis of rotation. This can be calculated by multiplying the lever arm and the force on the object. Torque = lever arm x force When the object balances the torque on each side of the object is the same. We now know hat the lever arm of the meter-stick is 30cm but we need to determine the force acting on the meter stick. The 100 gram mass is our force since gravity is acting on the mass. We can convert this mass to weight (a force) by multiplying the mass by gravity (9.8 N/kg). Since gravity is in kg we first must convert the grams into kg which is .98 kg. Now that we have determined our lever arm is 30cm and our force is .98 N/kg we can determine the toque on one side of the meter-stick thus allowing us to find the total mass of the meter-stick. Once my group made this calculation we discovered that the torque on the system is 29.4. Once we found the torque, we determined that since the lever arm was 30 cm we had to subtract this amount by the entire lever arm when no weight is added to the system. Since the system in in equilibrium at 50cm, we subtracted the 30cm by 50cm. 20cm is our new lever arms and is vital when deriving the mass of the meter stick. Since we know the total torque we can reorganize the equation in order to find the mass. This equation would be; Torque/Lever arm= Force Once we calculated that the force equated to 1.47 we needed to convert this number to grams. We were able to do this by dividing this value by 9.8 (the force of gravity) and then multiplying by 100. This equated to the value of 150g. Once we weighted the meter stick, my group discovered that the actual weight of the meter stick was 150.4 grams. Since our estimation was off by only 0.4 grams my group was amazed and in shock. The picture below will show you how to set up the experiment. I have indicated that 30cm is where our meter stick balanced however this is different for every meter stick.

Introduction to Torque

This video was very useful when understanding Torque. The video talks about center of gravity and gives demonstrations on torque. The video also defines Torque and provides the universal symbol. The video explains directions of torques and when to determine torque values as positive and negative. He also demonstrates an example when the net toque of an object is zero and how to determine the torque.

Merry-Go-Round

Now, although this looks a little fun it is a very bad idea. They used a motorcycle to increase the speed of the merry go round. Although they went very fast can you identify something that reduced their speed? Since the two individuals were sitting at the end of the wheel, the wheel had a higher rotational inertia and thus had a lower rotational velocity then if they moved to the middle. The two individuals lowered the rotational velocity as much as they could since they were located faraway from the axis of rotation.