In rotational mechanics, objects spin around an axis. Angular momentum is the measure of how much an object wants to keep spinning.

What is Angular Momentum?

Imagine a spinning top or a bicycle wheel. Angular momentum is a physical quantity that tells us how hard it is to stop that object from spinning. It depends on how fast the object rotates and how its mass is spread out from the center. If an object spins faster, it has more angular momentum. If it is heavier or wider, it also has more.

Defining Torque

Torque is a twisting force that makes an object rotate. Think of using a wrench to tighten a bolt. You apply a force at a distance from the center, which creates a twist. Without torque, a spinning object will keep spinning forever at the same speed. Torque is the only thing that can speed up, slow down, or change the direction of a rotation.

The Mathematical Connection

There is a direct link between these two concepts, which looks very similar to Newton’s second law for linear motion (Force = Mass × Acceleration). In rotational physics, the relationship is:

• Torque = Change in Angular Momentum / Change in Time

This means that if you apply a torque to a spinning object, its angular momentum changes over time. If the torque acts in the same direction as the spin, the object speeds up. If the torque acts against the spin, the object slows down.

Real-World Examples

A figure skater uses this relationship constantly. When a skater pulls their arms in, they change their distribution of mass, which forces their rotation speed to increase to conserve angular momentum. If they push their arms out, they apply a torque to themselves against the motion, slowing their spin down. This balance between torque and momentum governs everything from spinning planets to the wheels on your car.