2. Kinetic Friction

2.1: In this section, you will use the cart, track, protractor, and a stopwatch (phone, computer, watch). Tilt the track until the cart can accelerate down the track with no sticking. Measure or calculate the chosen angle of the track. Make sure that the friction pad is on (like in 1.4).

2.2: Draw another force diagram for this system like you did in 1.1 (but this time the cart will be moving down the track). Calculate how long it should take for the cart to reach the bottom of the track if you were to assume no friction acts on the cart. Use Newton’s 2nd Law to predict a value for the acceleration of the cart, then calculate t using 

2.3: Measure the time it takes for the cart to reach the bottom of the track. Take three total measurements, average the values, and estimate the uncertainty. Make sure to release the cart from the same place on the track each time. Compare your calculated value from 2.2 (where you assumed that there wasn’t any kinetic friction) with your measurement. Explain any differences or similarities.

2.4: Working backward from your measured times, calculate the acceleration your metal cart experienced as it traveled down the slope. Based upon this acceleration value, what is the magnitude of the kinetic friction force?

2.5: Based upon what you found for the kinetic friction force in 2.4, calculate the coefficient of kinetic friction (μk) of the cart/track interface. Compare this value to the value given for the coefficient of kinetic friction on the simulation.