**Design**

**Conservation of Energy and the Coefficient of Friction of a Hot Wheels Car**

Video

Procedure

1. We set up a ring-stand with a 61 cm long board resting on it with the Hot Wheels track taped down onto the board.

2. We then measured the height of the ramp and used that to do the inverse sine function to find the angle of the incline.

3. Then we connected the photo gate system to the laptop and placed the photo gate at the bottom of the ramp and placed rulers at either side of the track in order to maintain the photogate above the ramp.

Procedure Continued

4. We used the photogate system to find the final velocity of the car at the bottom of the ramp.

5. Then we drew a free body diagram of the car on the ramp.

6. We found the force of gravity and its perpendicular force, in order to find the normal force.

7. Then we found the initial gravitational potential energy and the initial kinetic energy.

8. Next we found the final values for both the GPE and the KE.

9. With this information we were able to use the equation of the work of friction to find the force of friction.

10. Now that we had the force of friction and the normal force we could find the coefficient of static friction by using the equation Ff/Fn.

Results

Vi = 0 m/s

Vf = .88 m/s

GPEi= .086 J

GPEf= 0 J

KEi= 0 J

KEf= .013 J

μ= .412

Free Body Diagram

Calculations

Static vs. Kinetic Friction

For this lab, we found the coefficient of static friction rather than the coefficient of kinetic friction based on their respective definitions. Friction is kinetic when two surfaces are sliding against each other. Friction is static when two objects are not moving relative to each other. In the case of the car and the track, because the wheels of the car are never sliding against the surface of the track, the car is not experiencing kinetic friction.

Conclusion

Calculations Explained

We first found the normal force on the car which we knew would be used later in the calculations to find the frictional force. We then found the initial Gravitational Potential Energy by using the equation GPE=mgh which we found to be .086 J. Based on our knowledge of energy, we were able to conclude that both the initial Kinetic Energy and the final Gravitational Energy would be equal to zero. We then found the final Kinetic Energy which was .13 J. Then, using the Work equation, we were able to find the force of friction on the system. Using the force of friction and the normal force, we were able to find the coefficient of friction.

The data collected in this experiment shows the effect that the coefficient of friction has on the total energy of a system. According to our data, the coefficient of friction has a substantial effect on the total energy.