Torque

High School

Definition

A turning effect produced by a force applied at a distance from a pivot, equal to the force multiplied by that distance. Torque causes rotation, which is why a longer wrench makes it easier to turn a stiff bolt.

Worked examples

\(\tau = F \times d = 50\,\)N\( \times 0.3\,\)m\( = 15\,\)N\(\cdot\)m\(\)

A 50 N force applied 0.3 m from the pivot produces 15 N·m of torque.

Using a 0.5 m wrench instead of a 0.2 m wrench with the same force produces 2.5× more torque.

Longer distance from the pivot multiplies the turning effect, making the job easier.

Common mistakes

\(\tau = F \times d\) where \(d\) is the total length of the wrench → \(d\) is the perpendicular distance from the pivot to where force is applied Only the perpendicular lever arm counts — the straight-line distance from the pivot point to the line of force.
Torque and force are the same thing → Torque is force times distance; it measures rotation, not just push or pull Force alone does not cause rotation — you need both force and distance from the pivot.
\(\tau = m \times a\) → \(\tau = F \times d\) (or \(\tau = I \alpha\) for rotational motion) Newton's second law for linear motion does not apply directly to rotation; torque replaces force and moment of inertia replaces mass.

Where you'll use it next

You'll use torque when studying rotational dynamics, analyzing levers and machines, balancing objects, and solving equilibrium problems in physics and engineering courses.

Found in 1 StudyPug lesson

Torque and Rotational Inertia: Foundations of Rotational Motion

Physics 12

Dive into the essential physics concepts of torque and rotational inertia. Understand their crucial role in rotating objects, from machinery to celestial bodies. Build a strong foundation for advanced mechanics and engineering applications.

12th Grade12th