Kinetic Energy

Part of the Mechanics section of Coddy's Physics journey. Lesson 51 of 97.

A moving object has kinetic energy, the energy of its motion:

$\mathrm{KE} = \frac{1}{2} m v^2$

It is never negative, and the direction does not matter: $5\ \mathrm{m/s}$ east and $5\ \mathrm{m/s}$ west give the same kinetic energy.

The speed is squared: twice the speed gives four times the kinetic energy.

Three identical 2 kilogram carts at 1, 2 and 3 metres per second, and below them bars of their kinetic energy: 1 joule, 4 joules and 9 joules

Kinetic energy of a $2\ \mathrm{kg}$ cart: twice the speed, four times the energy.

Challenge

A cyclist and her bike move at $6\ \mathrm{m/s}$ and have $1440\ \mathrm{J}$ of kinetic energy $\relax E_{k}$ together. Find their total mass $m$ .

Try it yourself

Solve for $m$

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Mechanics

1Introduction

4Inclined Planes

7Projectile Motion

10Work and Energy

13Impulse and Momentum

16Simple Harmonic Motion

3Friction

6Vertical Motion

9Project: Delivery Drone

12Elastic Energy

15Circular Motion

18Final Challenges