Humans can apply contact forces
to other humans
to the ground
and to
implements
(such as a bat or a racquet).
For movement to occur,
the force applied needs to be greater than the external forces acting on the human body.
For example,
if a footballer does not step hard into the ground,
he or she will not change direction to swerve around an opponent.
In the same way,
a long jumper will jump further by accelerating to the board and applying
a greater force to it than by running up
slowly and hitting the board with less
force.