Impulse

High School

Definition

The change in momentum produced when a force acts on an object over a period of time, equal to force multiplied by time. Increasing the time over which a force acts, as in a car's crumple zone, reduces the force needed for a given change in momentum.

Worked examples

\(J = F \Delta t = (50\,\)N\()(0.2\,\)s\() = 10\,\)N\(\cdot\)s\( = 10\,\)kg\(\cdot\)m/s\(\)

A 50 N force acting for 0.2 seconds delivers 10 kg·m/s of impulse, changing the object's momentum by that amount.

A gymnast bends her knees when landing to extend the stopping time from 0.05 s to 0.3 s.

By increasing the time sixfold, the force her legs must absorb drops to one-sixth—impulse stays the same.

Common mistakes

\(J = F \times d\) (using distance instead of time) → \(J = F \times \Delta t\) (force times time) Impulse depends on how long the force acts, not how far the object moves.
Longer impact time means greater impulse and greater force. → Longer impact time means same impulse but smaller force. For a fixed momentum change, stretching out time reduces the average force needed.
Impulse and momentum are different quantities with different units. → Impulse equals change in momentum; both have units kg·m/s (or N·s). N·s and kg·m/s are equivalent: impulse is literally the momentum change delivered.

Where you'll use it next

You'll apply impulse when solving collision and explosion problems in physics, designing safety features like airbags and helmets, and analyzing rocket propulsion and sports techniques that maximize or minimize force.

Found in 1 StudyPug lesson

Mastering Momentum and Impulse in Sports Physics

AS-Level Maths

Dive into the physics of ball kicks and racket hits. Learn to calculate impulse, analyze momentum changes, and apply these concepts to real-world sports scenarios. Boost your problem-solving skills today!

11th Grade11th