ROTATIONAL MOTION

Why is the concept of a couple important in practical applications like opening a bottle lid?

• Because it heats the lid
• Because it reduces friction
• It allows rotational motion without requiring the center of mass to move
• Because it breaks the seal

When is a rigid body said to be in partial equilibrium?

• When it is moving fast
• When it is at rest
• When it satisfies only one type of equilibrium—either translational or rotational
• When forces are zero

How does the application of a couple differ from a single force in terms of motion produced?

• Both cause only translation
• Both cause only rotation
• A couple causes rotation without translation, while a single force causes translation
• A couple causes translation, and a single force causes rotation

What is the significance of the midpoint C in torque calculations for a symmetric rod AB with CA = CB = a?

• It increases the force
• It has no role
• It is where mass is concentrated
• It is equidistant from both ends, making torque comparison symmetric and simple

Why can a body be in translational equilibrium but not in rotational equilibrium?

• Because forces are absent
• Because gravity is acting
• Because net force is zero but net torque is not zero
• Because the body is too light