Home   iit-jee  

Torque in Physics

Torque is a physical quantity in physics that describes the rotational effect of a force on an object. It is often referred to as the "rotational force" or "moment of force." Torque is essential for understanding the behavior of objects in rotational motion, such as the rotation of a wheel, the twisting of a screwdriver, or the operation of a wrench.

Definition of Torque

Definition of Torque (τ): Torque (τ) is the product of a force (F) applied to an object and the perpendicular distance (r) from the point of application of the force to the axis of rotation. Mathematically, it is expressed as:

τ = F * r * sinθ


Key Points about Torque

  1. Direction of Torque: Torque is a vector quantity with both magnitude and direction. Its direction is determined by the right-hand rule: If you curl your fingers in the direction of the force, the thumb points in the direction of the torque.

  2. Unit of Torque: The SI unit of torque is the newton-meter (N·m). In the Imperial system, it is often expressed in foot-pounds (ft·lb).

  3. Lever Arm: The lever arm (perpendicular distance) plays a crucial role in determining the torque's magnitude. The longer the lever arm, the greater the torque for the same force.

  4. Angle θ: The angle between the force vector and the lever arm is important. Torque is maximized when the force is applied perpendicular (90 degrees) to the lever arm (sin θ = 1). If the force is applied at an angle, the component of the force perpendicular to the lever arm is used to calculate torque.

Example of Torque

Consider the following example of a wrench being used to tighten a bolt:

To maximize the torque, you would:

This would result in a greater torque, making it easier to tighten or loosen the bolt.

In summary, torque is essential for understanding rotational motion and is influenced by both the force applied and the lever arm's length and orientation. It plays a crucial role in many everyday applications, from turning a doorknob to the operation of machinery.

Published on: Sep 18, 2023, 03:16 AM  


Add your comment