If an unbalanced force acts on an object its velocity will
change. We must now find out how this change can be made bigger and see what affects
how fast an object can be made to move.
A javelin thrower is a good example of a
force (arm muscles) being used to make an object (the javelin) move off as fast as
possible.
The bigger the force that the thrower uses the faster the javelin will go. But
why are you told to throw the javelin from behind you? This is so that the force in your arm is
pulling on the javelin for the longest possible time.
The change in velocity depends
on both the force and the time for which it acts.
We call the product of force and time the
IMPULSE. The bigger the impulse the bigger the change in velocity it will produce.