ROTATIONAL MOTION

How is the total external force related to the motion of the centre of mass?

• It determines the velocity directly
• It has no effect
• It determines the acceleration of the centre of mass according to F_ext = MA
• It only affects rotation

What happens to the centre of mass when a firecracker explodes in mid-air?

• It stops immediately
• It moves randomly
• It flies upward
• It continues along the original parabolic path

Why is the centre of mass unaffected by internal forces?

• Because internal forces are too weak
• Because they act only within molecules
• Because internal forces cancel out in pairs due to Newton’s third law
• Because they are balanced by friction

What does the term M in Eq. (6.7) represent?

• Mass of the first particle
• Reduced mass of the system
• Total mass of the system
• Average mass per particle

How is the acceleration of the centre of mass related to individual particle accelerations?

• It is the arithmetic mean of all accelerations
• It is always zero
• It is the mass-weighted average of the accelerations of all particles
• It depends only on the heaviest particle