#### IIT (NTSE/Olympiad)

# Circular Motion & Rotational Dynamics

__12. Forces Couple __

__12. Forces Couple__

**12. Forces Couple**

**(a)**When two forces of equal magnitude act on different points and in opposite direction, these force form a couple.

**(b)**The effect of couple is known by its moment.

**(c)**The moment of couple is equal to the product of magnitude of any force and perpendicular distance between the force.

Moment of couple = (F) (r)

**(d)**The couple causes the rotational motion in the body.

**(e)**Generally both couple and torque carry equal meanings.

When there is only one force applying on a body the reaction force forms torque with it.

**(f)**The work done by couple on a body is equal to work done by torque

∴ Work done by couple = work done by torque =

**(g)**If particle complete n rotations under the effect of couple or torque, work done W = τ (2 π n)

**(h)**As on stretching a spring energy is stored in it, in the same way as on twisting a wire the work done by torque is stored in the form of energy.

τ = C θ ¼Restoring torque½, (where C = twisting coefficient)

#### IIT (Class X)

- Unit, Dimension & Error

- Vectors

- Motion in One Dimension

- PROJECTILE MOTION

- NEWTON'S LAWS OF MOTION & FRICTION

- WORK, POWER, ENERGY & CONSERVATION LAWS

- CIRCULAR MOTION & ROTATIONAL DYNAMICS
- 1. Angular Displacement
- 2. Angular Velocity
- 3. Relation Between Linear Velocity And Angular Velocity
- 4. Angular Acceleration
- 5. Relation Between Angular acceleration and Linear Acceleration
- 6. Equation of linear motion and rotational motion
- 7. Centripetal Acceleration and centripetal Force
- 8. Type of Circular Motion
- 9. Banking of Tracks
- 10. Moment of Inertia (Rotational inertia)
- 11. Torque
- 12. Forces Couple
- 13. Angular Momentum
- 14. Kinetic Energy of Rotation
- 15. linear and rolling motion of a body on inclined plane
- 16. Points to Remember - Circular Motion & Rotational Dynamics

- GRAVITATION