Forces & Motion

Friction is the force that acts upon two surfaces that slide against each other.

If I use sandpaper to sand a plank of wood, friction is the force that works against my movement. 

Friction causes the melting of tectonic plates sliding against each other and can result in earthquakes.

An example of tension force, is the game tug of war. When two teams pull with equal force on a rope, the force transmitted through the rope is called tension. 

This pulling force can be on a rope, string, chain, rod or cable. 

Another example is a wrecking ball hung on a chain from a crane. The wrecking ball puts tension on the chain. 

Air resistance is the force applied to an object that is moving through air. It can also be called drag. When an object moves in one direction, air resistance or drag works against it in the opposite direction. 

A sky diver will experience air resistance when on a sky jump from a plane. 

A large bus will experience more air resistance than a streamlined car driving on a motorway. 

Spring force happens when a spring is compressed or stretched.

When you jump on a trampoline downward, the spring will push you back up with an equal force. 

The spring will always try to return to its original position.