Kinetic Energy (Edexcel IGCSE Physics)

Spec point — 3.14 · know and use the relationship: kinetic energy = 1/2 × mass × speed2 KE = 1 / 2 × m× v

Kinetic energy

• Energy in an object's kinetic store is defined as:

The amount of energy an object has as a result of its mass and speed

• This means that any object in motion has energy in its kinetic energy store

• Kinetic energy can be calculated using the equation:

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

• Where:

  • KE = kinetic energy in joules (J)
  • m = mass of the object in kilograms (kg)
  • v = speed of the object in metres per second (m/s)

Worked Example Calculate the kinetic energy stored in a vehicle of mass 1200 kg moving at a speed of 27 m/s.

Step 1: List the known quantities

• Mass of the vehicle, m = 1200 kg
• Speed of the vehicle, v = 27 m/s

Step 2: Write down the equation for kinetic energy

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

Step 3: Calculate the kinetic energy

K E=1 half×1200×(27)²

$KE=437400J$

Step 4: Round the final answer to 2 significant figures

$KE=440000J$

Exam Hint When performing calculations using the kinetic energy equation, always double-check that you have squared the speed. Forgetting to do this is the most common mistake that students make.