Force and Motion - How Do Force Works?

When do things move?

Things only move when a force is applied to them. Forces are pushes or pulls in a particular direction. A flag blows when the wind pushes it. A door opens when you pull it. Animals move when their feet push against the ground, their wings push against air or their fins push against the water around them.

How do forces work?

Forces work in pairs. They push or pull in opposite directions. When pairs of forces are equal they are said to be balanced. Tug-of-war teams remain still when each pulls with the same strength. A team falls when one side is stronger and the forces are unbalanced. Forces are also balanced when things move at on speed in the same direction. A rocket takes off when the force from the engine pushing it up is greater than the force of gravity pulling it down.

Did you know? Very fast cars, such as dragsters and rocket cars, need parachutes to slow them down quickly.

Why do thing stop moving?

Things slow down and stop because of an opposing force. One of these forces is friction. Friction happens when tiny bumps on two surfaces rub against each other. Rough surfaces, such as concrete, create more friction than smooth surfaces, such as glass. People use high-friction materials like rubber on shoe soles to stop people slipping when the walk.

How do parachutes work?

A parachute slows down a person's fall using 'air resistance'. Air resistance happens when air molecules in front of moving objects squash together and press back against it. The wide area of an open parachute creates lots more resistance than a person could create with his or her body alone. This reduces the following speed of the body.