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Non-Contact Forces
Students should be able to:
- identify contact/noncontact forces that affect motion of an object (e.g., gravity, magnetism and friction).
What is a force?
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.
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