An impulse is the measurement of how much a force changes an object's motion over a short amount of time.

In physics, when you push an object, you are applying force. If you apply that force for a very short duration, it creates an impulse. The impulse is calculated by multiplying the force applied by the time for which it acts. The mathematical formula is Impulse = Force × Time (I = F × Δt).

What is an Impulsive Force?

An impulsive force is a very large force that acts on an object for a tiny fraction of a second. Because the time is so small, the object experiences a sudden and massive change in its velocity (speed in a specific direction). These forces are common in collisions. For example, when a cricket bat hits a ball, the force exerted by the wood on the leather ball is an impulsive force.

The Relationship Between Impulse and Momentum

Momentum is defined as the product of an object's mass and its velocity. According to Newton’s second law, an impulse is equal to the change in momentum. This means that if you want to stop a moving object quickly, you must apply a large force over a very short time. Conversely, if you want to reduce the impact of a force, you increase the time over which the force acts.

Real-World Examples of Impulse

• Catching a Cricket Ball: When a fielder catches a fast-moving ball, they pull their hands backward. By moving their hands back, they increase the time (Δt) it takes for the ball to stop. This decreases the force felt by their hands.
• Car Crumple Zones: Cars are designed to crumple during an accident. This crumpling increases the time it takes for the car to stop. By stretching the time, the impulsive force on the passengers is reduced, which helps save lives.
• Hitting a Nail: A hammer hits a nail with a very large force for a very short duration. This allows the nail to drive into the wood instantly.