# Torque

The turning effect of a force, torque = r F sin theta. Longer lever arms need less force.

Physics (university) · Part 04: Rotation and gravity · Card 4 of 11 · Last updated 2026-10-19

## Analogy

A long spanner loosens a stuck nut more easily.

## Example

**Wrench**

tau = r F sin 90
tau = 0.3 x 100 x 1
tau = 30 N m

## In practice

A 100 N push at the end of a 0.3 m wrench gives 30 N m.

## Practice

### Flashcards

- **What is the unit of torque?** Newton metre (N m).

## Questions people ask

### Why is a door handle far from the hinge?

Torque equals force times distance from the pivot. Placing the handle far from the hinge gives a long lever arm, so a small push produces a large turning effect. Pushing close to the hinge takes much more force to open the door.

### Is torque a vector?

Yes. Its direction comes from the right-hand rule: curl your fingers the way the force turns the object, and your thumb points along the torque. At first-year level, you often treat torque as positive for anticlockwise turns and negative for clockwise ones.

## Related concepts

- [Angular velocity](https://studyvisually.com/learn/science/physics-university/physics-university-part-4/physics-university-part-4-concept-1)
- [Centripetal acceleration](https://studyvisually.com/learn/science/physics-university/physics-university-part-4/physics-university-part-4-concept-2)
- [Centripetal force](https://studyvisually.com/learn/science/physics-university/physics-university-part-4/physics-university-part-4-concept-3)
- [Moment of inertia](https://studyvisually.com/learn/science/physics-university/physics-university-part-4/physics-university-part-4-concept-5)

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