ROTATIONAL MOTION

Why can we ignore the details of internal forces when predicting CM motion?

• Because they are too small
• Because they are random
• Because their vector sum is zero due to Newton’s third law
• Because they are invisible

What is the implication of Eq. (6.11) for extended bodies?

• Rotation is eliminated
• Internal energy vanishes
• An extended body responds to external forces as if all mass were concentrated at the centre of mass
• Gravity becomes zero

What happens to the centre of mass when a person walks from one end of a boat to the other on still water?

• It moves forward
• It moves backward
• It oscillates
• It remains stationary if no external horizontal force acts

How is the centre of mass analogous to a single particle in motion?

• It has the same shape
• It rotates at the same rate
• It moves under external forces as if all mass were concentrated there
• It has zero energy

What is the role of external forces in changing the momentum of a system?

• They have no effect
• They stabilize momentum
• They are solely responsible for changing the total momentum
• They only affect individual particles