Calculate Kinetic Energy

What is kinetic energy?

Any object that is moving has kinetic energy. 

Kinetic energy (KE) depends on just two factors: mass and speed. The more massive an object is, and the faster it is moving, the more KE it has.

How is it calculated?

The equation for kinetic energy is:

KE = ½ m v² 

Where KE = kinetic energy, m = mass, and v = velocity (or 'speed').

As KE is a form of energy, its units are Joules. The equation only works if mass is in kilograms and velocity is in metres per second.

It is important to note that only velocity is squared in this calculation. The ½ and m do not need to be squared. These are just multiplied together, along with v². 

Let's do a quick example:

In a game of cricket, a child hits the ball, mass 500 g, at a speed of 10 m/s. How much kinetic energy does the ball have?

KE = ½ m v² 

KE = ½ x 0.5 kg x (10 m/s)² 

KE = ½ x 0.5 x 100 

KE = 25 J

Notice that we had to turn the mass into kilograms before putting it in to the equation, and only the speed had to be squared.

Now see if you can apply this equation in the questions in this activity.