ROTATIONAL MOTION

Why is the centre of mass important in analyzing motion of systems?

• Because it is always at rest
• Because it is easy to calculate
• It simplifies the analysis by reducing the system to a single effective point
• Because it is the geometric centre

What is the effect of internal forces on the total momentum of a system?

• They increase it
• They decrease it
• They do not change the total momentum
• They reverse its direction

How is Newton’s second law applied to a system of particles?

• As F = mv
• As F = dp/dt for each particle
• As M = A F_ext
• As τ = dL/dt

What is the basis for treating an extended body as a point mass at the centre of mass?

• Because it simplifies calculations
• Because the body becomes smaller
• The translational motion of the body is the same as if all mass were concentrated at the centre of mass
• Because gravity acts only at the centre

What happens when the net external force on a system is zero?

• The system stops moving
• All particles come to rest
• The centre of mass does not accelerate
• The system explodes