Imagine that you and a friend are
tossing a baseball. When you throw the ball it leaves your hand going
fast and, if your friend is far enough away, will eventually slow down
enough to fall to the ground. Why doesn't the ball continue in the same
direction forever? What causes it to fall to the ground?
The answer is that there are many
forces acting upon the ball that make it fall to the ground. A
force is a push or pull. Forces make things speed up, slow
down, and change direction. When you throw the baseball, you are applying
a force to it. When your friend catches the ball, they are also applying
a force to it to make it stop. But there are also many forces acting
on the ball in between you and your friend. They are non-contact and
contact forces.
Non-contact
forces
While the ball is
in the air, one force acting on it is gravity. Gravity
pulls the ball down to the earth without touching it. This means it
is an example of a non-contact force, or a force exerted on an object
that does not make contact with it. Another example of a non-contact
force is magnetism. Read more about magnetism.
Contact
forces
There is another forces
acting on the ball while it is in the air. While the ball travels to
your friend, it is experiencing air resistance. You
have experienced air resistance before: while sticking your hand out
of the window of the car or riding your bike into the wind. Air resistance
is an example of a contact force. The air is actually in contact with
the ball and slows it down. Another example of a contact force is friction.
Read more about friction.
