Forces and Motion

In everyday terminology the word 'Force' is used to describe something which involves a great effort. Sometimes it is used as a verb: 'he/she forced me to do it.' In Science, however, Force has a very specific meaning : it is a push or a pull. There are many and varied examples in our everyday lives and they can involve large or small pushes and pulls (e.g. pushing a car, pulling a rope, throwing a javelin). If we are going to think about forces and motion then we need to specify direction. We measure forces in "Newtons" (N).

Friction is a force that opposes motion. Friction acts in a direction opposite to the object's direction in motion. Without friction, the object would continue to move at a constant speed forever. There are different forms of friction.

One type is called sliding friction. This is when two surfaces slide one over the other. A snowboarder slides over the snow covered slopes using sliding friction everyday.

When an object rolls over a surface, the kind of friction that occurs is rolling friction. Skate boarders take advantage of this type of friction all the time. Reducing the amount of friction between the surface and the wheels allow skaters to go really fast.

Friction also occurs in fluids (gases and liquids). This is how a surfer glides over the water or a shark glides through the water. This type is called fluid friction.