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Forces and Motion

Is Friction Good or Bad?

Can Friction be a Bad Thing?

Friction can be bad. Whenever an object is moving,
for example a bicycle, car, train etc., friction provides an
opposing force which tries to slow the object down.
The largest type of opposing force
for the examples in the list above is air resistance.

What is Air Resistance?

Air resistance is a form of friction occurring where the object
is pushing air out of its way as it moves forward.
Air resistance causes kinetic energy to be transferred into heat.
If an object is moving very fast (for example a meteor)
the amount of heat can be so great that the object burns up.

How can Air Resistance be Changed?

Air resistance can be reduced by changing the shape
of the object so that it can push the air away more easily.
This is called streamlining.
The faster an object is moving, the more air resistance it
meets and so streamlining becomes more important
at higher speeds. A rocket is more streamline than a bus.


A small friction force comes from the solid mechanical surfaces
rubbing over each other in engines and wheel bearings.
This friction is kept small by lubricating the surfaces (oil them).

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