1. Forces

2. Effects of forces Forces can cause diverse effects on objects: – They make things start to move. – They make things stop. – They disfigure things. – They break things.

3. Forces and Motion Once an object is put in motion, it will not stop moving until another force acts to stop it. Objects can be stopped by another object. (For example: catching a ball.) Objects can be slowed to a stop by friction. (For example: grass can act as friction.)

4. Friction Surface resistance to a moving object. Brakes on a car or a bike create friction to quickly stop.

5. How Forces Act Normally, forces appear when two objects come in contact with each other. Other forces act without contact. For example, magnets can create movement (attraction or repulsion) without touching another object.

6. The Force of Gravity Gravity is the force that keeps objects on Earth. Gravity acts on all objects at all times. The force of gravity is what makes objects fall down.