Torque

Rotational Motion of Class 11

Torque is the rotational analog of force.

Force causes linear acceleration; torque causes angular acceleration.

In order to lift a stone by using a lever, a force is required (see figure 10.12). The effectiveness of the force depends both on its direction and where it is applied relative to the pivot point.

Torque

The turning ability of a force about an axis or pivot is called its torque.


The torque of a force F that acts at a distance r from the origin is defined as

 T = rF sinθ (10.20)

Where θ is the angle between the vector r and F, as shown in the figure (10.13).

Torque

The definition of torque (equation 10.20) may be interpreted in two ways:

(i) T = r (Fsinθ) = r  ⊥ F

The turning effect of a force about the origin is produced only by the perpendicular component (F⊥ = F sin θ) as shown in the figure (10.8 b).

(ii) T = (r sinθ) F = r F

Where r⊥ is the perpendicular distance from the origin to the line of action of the force as shown in the figure (10.8 a). It is also called the lever arm.

Torque

 

Talk to Our counsellor