1.1.3 Kinetic Energy

Kinetic Energy

• The kinetic energy (Ek or KE) of an object (also known as its kinetic store) is defined as:

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

• This means that any object in motion has kinetic energy

• Kinetic energy can be calculated using the equation:

Ek = ½ × m × v2

• Where:
• Ek = 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

Ek = ½ mv2

Step 3: Calculate the kinetic energy

Ek = ½ × 1200 × (27)2 = 437 400 J

Step 4: Round the final answer to 2 significant figures

Ek = 440 000 J

Exam Tip

When calculating kinetic energy, make sure you know that only the speed is squarednot the mass or the ½

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