### KS3 Physics

Energy
Motion and Forces
Waves
Electricity and Electromagnetism
Matter
Space Physics

# What Are Forces?

Forces change the speed, shape and direction of almost everything.

Whenever you push or pull, that can be described as a force. Forces take place all around us. Even though they are invisible, we can still see their effects in the environment.

As you can see in the image below, water is falling out of the bucket due to the force acting upon it. That force is gravity, which pulls the water out of the bucket and down towards the ground. Forces change the speed and direction of movement.

If gravity were not present:

## How exactly do we measure force?

Force is measured in newtons (N). For example, the force exerted on a spring could be 10 N. The greater the force, the more the spring stretches. Therefore, we can measure the force by measuring the extent of the stretch.

The image above shows a force meter, also known as a newton meter.

When an object is attached to the hook, the spring stretches. So, the heavier the object is, the longer the spring will stretch, which will provide a bigger reading.

## Forces Can Be Described as Pushes or Pulls

When a force is applied, it can alter the object’s direction of movement, speed and shape. This concept applies to contact forces (where an object must touch another object to exert a force).

• For example, when a door is pushed open, a force is applied, which causes the door to open.

A non-contact force is a force that acts on an object without physically touching it.

### Examples of non-contact forces

• Magnetic forces
• Gravitational forces
• Electrostatic forces (forces that electric charges exert on each other)
• Nuclear forces
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