Chapter 4.2, Problem 1aT

A ruler is placed on a pivot and held at an angle as shown at right. The pivot passes through the center of the ruler.

Predict the motion of the ruler after it is released from rest. Explain your reasoning.

Check your prediction by observing the demonstration.

1. Is the angular acceleration of the ruler in a clockwise sense, in a counterclockwise sense, or zero? Explain how you can tell.

What does your answer imply about the net torque on the ruler about the pivot? Explain.

2. What is the direction of the acceleration of the center of mass of the ruler? If ${\stackrel{\to }{a}}_{\text{cm}}=0$ , state that explicitly. Explain how you can tell.

What does your answer imply about the net force acting on the ruler? Explain.