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# 11: Rotational dynamics

Learning Objectives

• Understand how to use vector quantities for describing the kinematics of rotations.
• Understand how to use torque to determine the angular acceleration of an object.
• Understand conditions for static and dynamic equilibrium.
• Understand how to determine the moment of inertia of an object.

In this Chapter, we use Newton’s Second Law to develop a formalism to describe how objects rotate. In particular, we will introduce the concept of torque which plays a similar role to that of force in non-rotational dynamics. We will also introduce the concept of moment of inertia to describe how objects resist rotational motion.

prelude

A construction worker would like to lift one end of a heavy block from the ground using a bar propped against a rock on the ground as a lever. Should he place the rock close or far from the block to make it easier to lift the block?

1. It will be easier to lift the block if the rock is close to the block.
2. It will be easier to lift the block if the rock is far from the block.
3. It does not matter where he places the rock, as long as the bar is short.
4. It does not matter where he places the rock, as long as the bar is long.