PHYSICS – ROTATIONAL MOTION
■ SUPER DETAILED NOTES | Class 11 | 100/100 Boards Oriented
1. Introduction to Rotational Motion
Rotational motion is the motion of a rigid body in which every particle of the body moves in a
circular path about a fixed axis. Unlike translational motion, different particles have different
linear velocities but same angular velocity.
Examples include rotation of ceiling fan, wheels of vehicles, spinning top, and Earth rotating
about its axis.
, 2. Torque (Moment of Force)
Torque is the turning effect produced by a force about an axis of rotation. It determines how
effectively a force can rotate a body.
Mathematical Expression:
τ = r × F = rF sinθ, where r is position vector and θ is angle between r and F.
Factors affecting torque:
1 Magnitude of applied force
2 Perpendicular distance from axis
3 Angle of application of force
Short Questions:
1 Why does a longer spanner make it easier to loosen a nut?
2 Can torque be zero even if force is non-zero? Explain.
■ SUPER DETAILED NOTES | Class 11 | 100/100 Boards Oriented
1. Introduction to Rotational Motion
Rotational motion is the motion of a rigid body in which every particle of the body moves in a
circular path about a fixed axis. Unlike translational motion, different particles have different
linear velocities but same angular velocity.
Examples include rotation of ceiling fan, wheels of vehicles, spinning top, and Earth rotating
about its axis.
, 2. Torque (Moment of Force)
Torque is the turning effect produced by a force about an axis of rotation. It determines how
effectively a force can rotate a body.
Mathematical Expression:
τ = r × F = rF sinθ, where r is position vector and θ is angle between r and F.
Factors affecting torque:
1 Magnitude of applied force
2 Perpendicular distance from axis
3 Angle of application of force
Short Questions:
1 Why does a longer spanner make it easier to loosen a nut?
2 Can torque be zero even if force is non-zero? Explain.
