1. Newton’s First Law of Motion

2. Introduction It is an everyday experience that if you push or pull a stationary object it will start to move. It is also our experience that it is more difficult to start larger objects (like railway carriages) moving than small ones (like tennis balls). It is also more difficult to get an object to move fast (or to stop it when it is moving fast) than to get the same object to move slowly (or to stop it when it is moving slowly).

3. Introduction Cont. In the late sixteenth century, Galileo Galilei began formulating rules to describe these experiences more precisely. Sir Isaac Newton later formulated his own observations and insights as well as those of his predecessors into three laws of motion.laws of motion These laws describe how bodies respond to forces and are known as Newton’s Laws of Motion. They are only justified because they lead to results which are consistent with our observations.

4. Galileo

5. Sir Isaac Newton

6. Newton’s First Law of Motion An object at rest remains at rest and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.

7. Part 1: Objects at Rest An object that is not moving is said to be an object at rest. Objects at rest will remain at rest unless they are acted on by an unbalanced force. Objects will not start moving until a push or pull is exerted on them. Examples: airplanes, chairs, golf balls

8. Part 2: Objects In Motion An object moving at a certain velocity will continue to move forever at the same speed and in the same direction unless some unbalanced forces acts on it.

9. Friction It is a common experience that objects do not continue moving indefinitely once they are set in motion. This is because of the force of friction. In order to start an object moving it is necessary for the applied force to exceed the force of friction.

10. Notebook Activity

11. Inertia The tendency of a body to remain at rest or to continue moving in a straight line is called its inertia. An object with a small mass has less inertia than an object with a large mass. Example: softball vs. bowling ball

13. Ticket Out The Door On a half sheet of paper answer the following question in a complete sentence: When you stand while riding a bus, why do you tend to fall backward when the bus starts moving?