Question

Joseph, Winston, and Franklin are doing an experiment in lab that involves rotational dynamics. Using the apparatus below, Joseph places a disk with a mass of 379 g on the apparatus. Winston then hangs a 15 g mass from the pulley and releases it. The 15 g mass drops and then rises back up, then drops again. They each graph the angular velocity was a function of time as the hanging weight drops, rises, and drops again. Their graphs are shown below. Only one is correct. Identify the correct graph and explain why it is correct. (10 pts). For the incorrect graphs, explain why they are not correct. (two explanations at 10 pts each = 20 pts for this portion; 30 pts total.)

Answer 1

Correct graph is shown above.

In the graph, magnitude of angular velocity i s plotted

Initially angular velocity of disk increases at constant rate , due to constant acceleration of 15 g mass block.

When the 15 g mass hitting the floor then bounce back due to its kinetic energy,

at that time angular velocity decreases from maximum to minimum.

After reaching the initial height, again 15 g mass is falling down due to gravity.

Hence angular velocity of disk increase from minimum to maximum again