1. Chapter 16 Notes

2. Objectives 1. Describe the effects of gravity, friction, and centripetal force. 2. Explain the difference between weight and mass. 3. Describe Newton’s three laws

3. Objective 1: Describe the effects of gravity  Force applied = the object is pushed or pulled  Force that attracts 2 objects together is gravity  The 2 things that changes the effects of gravity are:

4. 1) The mass of the objects  As the mass increases the gravity increases

5. 2) The distance between the objects  As the distance increases the gravity decreases

6. Objective 1: Describe the effects of friction  Friction = force that slows motion or prevents it  3 types: 1. Rolling friction Wheels travel over distance The rougher the surface = greater friction

7. 2.Sliding friction Is increased with an increase in traction

8. 3.Fluid friction Is increased with an increase of surface area of object Includes water and air

9.  The amount of friction can be reduced by using lubricant example: grease and oil

10. Objective 1: Describe the effects of centripetal force.  All moving objects travel in a straight path, unless acted upon by an outside force  Centripetal force causes an object to follow a curved path

11.  Example: Turning a corner – car is centripetal force  Example: spinning a ball from a string – string is centripetal force

12. Discovery Video  http://10.20.0.2/videos/1/11883/pg r11883_1000k.wmv http://10.20.0.2/videos/1/11883/pg r11883_1000k.wmv

13. Objective 2: Explain the difference between weight and mass.  Weight = force of gravity on an object  Weight changes, while mass stays constant  The pull of gravity is greatest at the poles

14. Objective 3: Describe how inertia affects an object’s weight  Sir Isaac Newton contributions 3 laws of motion: 1. Law of inertia 2. Law of acceleration 3. For every action there is an equal and opposite reaction

15. Discovery Education Video Basics of Physics: Newton's Laws of Motion

16.  Law of inertia – an object at rest/motion will stay at rest/motion unless acted upon by a force

17. Example: a person in a car stays in motion after a car wrecks which causes the person to be flown forward, until it is acted upon by another force (airbag)

18.  Inertia is property of matter  Increase mass: increase inertia Ex. It takes a stronger force to stop a larger object

19. 2.Law of acceleration  Acceleration = force ÷ mass  Force = mass X acceleration   Mass  Force for the same acceleration

20. 3. Newton’s 3 rd law  For every action there is an equal and opposite reaction