Torque

Science

Definition

The rotational equivalent of force — a measure of how much a force causes an object to rotate around an axis. Torque depends on the magnitude of the force, the distance from the axis of rotation (lever arm), and the angle at which the force is applied.

Examples

  • Using a longer wrench handle makes it easier to loosen a bolt because torque increases with lever arm length
  • A door is easiest to push open at the handle (far from hinges) rather than near the hinges
  • A seesaw balances when the torques on each side are equal (heavier person sits closer to the pivot)
Key Fact

τ = rF sin θ, measured in newton-meters (N·m). Net torque = Iα (moment of inertia × angular acceleration).

Related Terms

Rotational inertia Angular velocity Net force Work

Study This Concept

Practice torque with free review games in these units:

AP Physics 1 Unit 5: Rotational Motion