Your name: _____________________

Print this page, record your answers on it, and show it to your lab TF at the start of your lab session.
This is the rotational equivalent of the "Motion with Constant Acceleration" experiment - review that before doing this one. In this experiment you will investigate moments of inertia by applying a torque to a disk that is free to rotate. The torque comes from a string wrapped around a pulley on the disk; the string passes over a second pulley and has a mass hanging from it.
We'll start by deriving equation (3) from the lab write-up. The simulation should be helpful.

Sketch a free-body diagram for the hanging mass m. The mass accelerates down when the system is released from rest. Apply Newton's Second Law to find the relationship between T, the tension, and a, the acceleration.

What is the connection between α, the angular acceleration of the disk, and a?

Show how combining your two equations above with equations (1) and (2) in the lab manual will give you equation (3) in the manual.

The tension is not the only force producing a torque. There is also a frictional torque present that opposes the disk's motion (this is minimized by supporting the disk on a cushion of air). Use the "Top View" of the experiment in the simulation to answer the following questions.

When the mass is falling, and the disk is speeding up, how does the direction of the frictional torque compare to the direction of the torque from the string?