# Work done by Couple | Physics Grade XI Rotational Dynamics Reference Note

### work done

☰   Related Articles

#### Kinematics

Introduction to Kinematics

#### Viva Voice Questions # Work done by Couple

Work done by couple
Two equal and opposite parallel forces acting on a rigid body at different points constitutes a couple. Consider a wheel of radius r rotating about its center O. Suppose two unequal forces F act tangentially at points A and B of a diameter of the wheel as shown in the figure. Let θ be the angle of rotation of the wheel. The couple or torque due to the forces are constant.

The work done by each force = force * distance
= F * s
= F * r. θ
Where θ is in radian and distance = AA' = BB' = s = rθ
.: total work done W = F * r. θ + F * r. θ = 2 F r. θ

But torque, τ = F * 2r = 2Fr
So, W = τθ

Therefore, work done by couple is the product of torque and angle of rotation of a rigid body.

For power, according to definition,
P = dW/ dt = d (τθ)/ dt
= τ dθ/ dt
= τω

## Popular Subjects

Join with us on social media to see our updates on your feed.