1. Gravity is a force exerted by masses.
Chapter 3.1

2. 3.1 Gravity is a force exerted by masses.
Greater mass results in greater force.
Greater distance results in smaller force.

3. Gravity on Earth
Earth’s gravity exerts a downward pull on a dropped coin.
Newton’s Third law
For every action there is an equal and opposite reaction.
The coin is also pulling on the earth, you don’t notice it because of the force of the earth.

4. Gravity on Earth
The force of the earth causes things to accelerate toward it, this is called g.
When there is no air pressure all falling objects fall at the same rate (g).
g = 9.8 m/s2 on earth
Newtown Second Law
F=ma
F=mg

5. Gravity on Earth F=mg
If a 30kg objects falls from the top of a building, how much force is acting on the object?
F= mg
F= 30 x 9.8
F= 294N

6. Gravity on Earth
Does the horizontal movement cause an object to take longer to drop?

7. Acceleration due to gravity
Different Masses
Horizontal Direction

8. Weight and Mass Weight and Mass are not the same.
Weight: the force of gravity on an object.
Mass: A property an object has no matter where it is located.

9. Orbit: p. 81
An object in orbit, like an object falling to the ground, is pulled toward the Earth’s center. If the object moves far enough forward as it falls, it orbits around the Earth instead of hitting the ground.
Held in a circle by centripetal force.