Torque Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Torque.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The rotational equivalent of force; a measure of how much a force tends to cause an object to rotate about an axis.

How hard you're twisting something. Depends on force AND distance from pivot.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Torque = force \times lever arm (perpendicular distance to the axis).

Common stuck point: Torque is not force—same force at different distances produces different torques.

Sense of Study hint: When solving a torque problem, first identify the pivot point (axis of rotation) and each applied force. Then calculate each torque as \tau = rF\sin\theta, where r is the distance from the pivot and \theta is the angle between the force and the lever arm. Finally, assign positive/negative signs for counterclockwise/clockwise and sum all torques.

Worked Examples

Example 1

easy
A force of 20 \text{ N} is applied at the end of a 0.5 \text{ m} wrench, perpendicular to the wrench. What is the torque produced?

Solution

  1. 1
    Torque is the rotational equivalent of force: \tau = rF\sin\theta.
  2. 2
    Since the force is perpendicular to the lever arm, \theta = 90° and \sin 90° = 1.
  3. 3
    \tau = rF = 0.5 \times 20 = 10 \text{ N m}

Answer

\tau = 10 \text{ N m}
Torque measures the tendency of a force to cause rotation. It depends on the force magnitude, the distance from the pivot point, and the angle between the force and the lever arm.

Example 2

medium
A 3 \text{ m} seesaw has a pivot at its center. A 30 \text{ kg} child sits at one end. How far from the center must a 45 \text{ kg} child sit to balance the seesaw? Use g = 9.8 \text{ m/s}^2.

Example 3

medium
A 30 N force is applied at the end of a 0.4 m wrench at 60\u00b0 to the handle. Calculate the torque.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
A door (1 \text{ m} wide) requires 50 \text{ N m} of torque to open. What force must be applied at the edge of the door, perpendicular to it?

Example 2

hard
A 40 \text{ N} force is applied to a 0.8 \text{ m} lever arm at an angle of 60° to the lever. What is the torque? How does this compare to the maximum possible torque with the same force?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

forcecircular motion