1. Relating Gravitational Field Strength to Gravitational Force
Physics 20
Relating Gravitational Field Strength to Gravitational Force

2. Gravitational Acceleration
Can be calculated at any point in the universe just by knowing the formula for weight and the formula for Newton’s Law of Gravitation.
Weight = Fg = mg
Newton’s Law of Gravitation = Fg = Gm1m2 r²

3. Gravitational Acceleration and weight
Knowing this we can now calculate our mass and the gravitational force acting on us anywhere in the universe.
Example: Pg 218 text
A) Calculate the magnitude of the gravitational acceleration of an object at the equator on the surface of the earth and the moon.
B) Determine the ratio of gearth and gmoon. How different would you weight be on the moon?
Remember: mass is a scalar quantity and does not depend on location

4. True vs. Apparent weight
Elevator Example: pg
True weight happens when Fn = Fg
Happens when gravity is the only acceleration acting on you,
Apparent weight Fnet = Fg +Fn
Happens when there is an acceleration acting on an object in addition to gravity.
Draw free body diagrams to show

5. Example – Pg 224 text
A kg astronaut is a spacesuit is standing on a scale in a rocket. The acceleration of the rocket is 19.6 m/s² up. Calculate her true weight and apparent weight during liftoff on earth.

6. Assignment Reading Questions Pearson Physics Pages 216 - 229
Pg 229 text: #’s 2, 5, 7, 8, 9