# 5.2.2 Kinetic Energy

### Derivation of KE = 1/2mv2

• Kinetic energy is energy an object has due to its motion (or velocity)
• A force can make an object accelerate; work is done by the force and energy is transferred to the object
• Using this concept of work done and an equation of motion, the extra work done due to an object’s speed can be derived
• The derivation for this equation is shown below:

Derivation for Kinetic Energy equation

### Kinetic Energy

• Kinetic energy is energy an object has due to its motion (or velocity)
• The faster an object is moving, the greater its kinetic energy
• When an object is falling, it is gaining kinetic energy since it is gaining speed. This energy transferred from the gravitational potential energy it is losing
• An object will maintain this kinetic energy unless its speed changes

Equation for Kinetic energy

KE: The energy an object has when its moving

#### Exam Tip

When using the kinetic energy equation, note that only the speed is squared, not the mass or the ½.

If a question asks about the ‘loss of kinetic energy’, remember not to include a negative sign since energy is a scalar quantity.

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