ROTATIONAL MOTION

How does an acrobat perform mid-air rotations without external torque?

• By pushing air
• By using gravity
• By changing mass
• By changing body configuration to alter moment of inertia

What is the basis for deriving τ = Iα using work-energy principles?

• From gravitational potential
• From linear motion analogy
• Consistency with rotational kinetic energy change
• From frictional loss

What does the constancy of L⊥ imply in fixed-axis rotation?

• Rotation is unstable
• Precession occurs
• No rotational change occurs in perpendicular directions
• Torque is maximum

What is the direction of the angular momentum vector for a symmetric body rotating about a fixed axis?

• Perpendicular to the axis
• Random direction
• Along the axis of rotation
• Opposite to velocity

For symmetric bodies, how is total angular momentum related to Lz?

• L = 0
• L = L⊥
• L = Lz k̂
• L = 2Lz