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!