What are forces?

Forces act on you all the time.

If you surf, you can feel many forces pushing and pulling you in different directions. Gravity always pulls you down, towards the Earth. This force can be balanced by the force of the surfboard acting upwards. Forces of the waves push you towards shore and friction from the air and the water pull you back out to sea. Surfing requires your body to balance all those forces acting on you. If they are not balanced, you will fall.

Things that are moving continue to do so unless a force makes them stop.

The force that makes most moving objects stop is friction. Friction exists whenever two surfaces are in contact. Friction is the force that provides the grip needed by cars, bikes, trucks and your shoes to start moving, change direction and slow down. Friction can be a problem. It causes machines with moving parts to heat up, which wastes energy.

On the Giant Drop at the Gold Coast’s Dreamworld, passengers fall 120 metres in 5 seconds, reaching speeds of 135 km/h. A magnetic braking system stops them just before they hit the ground. In everyday life, we don’t experience gravity quite as dramatically as these passengers, but you do feel its effects constantly.

A non-contact force acts through a region of space called a force field.

When you drop an object, it is pulled towards the Earth due to the Earth’s gravitational force field. A balloon can be charged and attract a thin stream of water that lies within its magnetic field. A magnet can attract a tub of nails if they lie within its magnetic field. Powerful electromagnets can lift heavy steel.

(Rickard, Devlin, Linstead, Madden, & Spenceley, 2013, pp. 277, 288, 297, 305)