Two cylinders of the same mass and shape, one hollow and one solid, are set on a incline and allowed to roll down. Which cylinder will reach the bottom of the incline first? Why?

A simple pendulum of mass m on a string of radius r is displaced from vertical by an angle θ, as shown below. What is the torque provided by gravity at that point?

See the last problem. What is the angular acceleration of the pendulum at that point?

A revolving door is common in office buildings. What is the magnitude of the torque exerted on a revolving door of mass 100 kg if two people push on opposite sides of the door with a force of 50 N at a distance of 1 m from the axis of the door, as shown below? Also, the moment of inertia of a revolving door is given by I = . Find the resultant angular acceleration assuming no resistance.