In this project, I will research how the location of the brick in LEGO cars affects how fast they go down a ramp. I think that the wind resistance will make the speed of the LEGO cars the same no matter what the design is.
For the experiment, I made a ramp out of three books. The ramp was 6.1 cm high and at an angle of 13 degrees. I measured how long it took a LEGO car to roll from the top of the ramp to a finish line about 30 cm from the ramp. For the experiment I made three LEGO cars using the same bricks. Each car weighed 35 g. Car 1 had most of the bricks at the back. Car 2 had most of the bricks in the front. Car 3 had most of the bricks in the middle. I measured the time it took for the cars to go down to ramp to the finish line four times each. I found the average for each car and compared them. Pictures of the cars and the ramp are below.
For the experiment, I made a ramp out of three books. The ramp was 6.1 cm high and at an angle of 13 degrees. I measured how long it took a LEGO car to roll from the top of the ramp to a finish line about 30 cm from the ramp. For the experiment I made three LEGO cars using the same bricks. Each car weighed 35 g. Car 1 had most of the bricks at the back. Car 2 had most of the bricks in the front. Car 3 had most of the bricks in the middle. I measured the time it took for the cars to go down to ramp to the finish line four times each. I found the average for each car and compared them. Pictures of the cars and the ramp are below.
How it works
When a car is at the top of a ramp (like a sled at the top of a hill), it has potential energy from gravity. "Potential energy is energy something has because of its position (Clark, p. 27)." The potential energy depends on the height of the car and its weight. Kinetic energy is the energy of motion, so it is the form of energy possessed by anything that is moving (Clark, p. 27)." The kinetic energy of the car at the top of the ramp is zero because it's not moving. When the car moves down the ramp, it gains kinetic energy and loses potential energy. At the bottom of the ramp, all the potential energy has turned into kinetic energy. "The higher the car, the faster gravity makes it go and the farther gravity makes it travel (Tocci, p. 31)." The height of the car depends on the center of mass of the car. "The point at which all of an object's mass appears to me concentrated is called the center of gravity (also sometime called the center of mass) (Clark, p. 33)." The center of mass is where the car would balance on my finger. A car with a center of mass towards the back is higher on the ramp than a car with the center of mass towards the front.
Results
I had expected wind resistance to make all the cars take the same time. I found that center of mass controlled the time. Car 1 went fastest and had all its weight on the back. Car 2 went the slowest and had all its weight on the front. Car 3 was in the middle and had all its weight in the middle. I would not have been able to tell which car went fastest if I had not taken an average because all the times are close.
I think it turned out differently than I thought because they were not close in speed.
I think it turned out differently than I thought because they were not close in speed.
Sources
Physics Matters! John O.E Clark ed.
Expieriments with gravity by Salvatore Tocci
Expieriments with gravity by Salvatore Tocci