1. Friction, Inertia and Gravity

2. Definition Important Info Friction Inertia Gravity
Warm-up Activity (Week 7) 12/5/11 Draw the following Chart (Landscape):
Definition
Important Info
Friction
Helpful-
Harmful-
Reduced-
Inertia
Greater Mass-
More Inertia-
Greater force to change motion-
Gravity
Law of Universal Gravitation
Gravitational Acceleration-

3. Essential Question
How would motion change if inertia, gravity and friction did not exist?

4. Definition of Friction
A force that opposes motion between two surfaces that are in contact.
Friction occurs because the surface of any object is rough.

5. FRICTION The amount of friction depends on many factors including:
the force pushing the surfaces together
the roughness of the surfaces.

6. HOW CAN FRICTION BE HELPFUL?
In order to walk, the foot must be able to push off against the ground.

7. HOW CAN FRICTION BE HARMFUL?
The thermal energy produced by friction can heat up a car engine

8. HOW CAN FRICTION BE REDUCED?
Friction can be reduced by using lubricants like oil.

9. Definition of Inertia
The tendency of all objects to resist any change in motion.
Inertia has a direct or linear relationship to mass. The greater the mass of an object, the greater the inertia of an object.

10. INERTIA
Because of inertia, an object at rest will remain at rest until a force makes it move.
Likewise, inertia is the reason a moving object stays in motion with the same velocity unless a force changes its speed or direction.

11. LET’S CHECK FOR UNDERSTANDING!!!
1.Which has a greater mass – a bowling ball or a ping-pong ball?
A Bowling Ball
2.Which has more inertia– a bowling ball or a ping-pong ball?
3.Which will require more force to change its motion – a bowling ball or a ping-pong ball?

12. GRAVITY – Force of Attraction
Definition of Gravity: The force of attraction between any two masses

13. Characteristics of Gravity
Gravity depends on the masses of the two objects and the displacement between them.
One of the weakest forces in the universe
Force exerted by every object in the universe on every other object

14. Law of Universal Gravitation
All objects in the universe attract each other through gravitational force. The size of the force depends on the masses of the objects and the distance between the objects.
Gravitational Force Increases as Mass Increases
Gravitational Force Decreases as Distance Increases

15. Gravitational Acceleration

16. Consider the following:
Will a feather and a hammer fall at the same rate here on Earth? On the moon?

17. Consider the following:
Will a feather and a hammer fall at the same rate here on Earth?
The feather and the hammer will not fall at the same rate on Earth because of the friction caused by our air will slow the feather down.

18. Consider the following:
Will a feather and a hammer fall at the same rate here on the moon?
The feather and the hammer will fall at the same time on the Moon because the moon does not have an atmosphere...no friction