1. Experiencing Gravity’s Effects

2. Review: Symbols and Language
Stands For
Meaning Fg
Gravitational Force
This is the magnitude of the gravitational force on an object, which can also refer to the weight of an object. g
Acceleration due to Gravity
This is the amount of acceleration that an object experiences because of the gravitational force acting on it at a certain point, usually related to a certain planet. G
Universal Gravitational Constant
This is the number that we multiply with to convert the product of the masses and the inverse square of the distance into a force, measured in units of Newtons.

3. Acceleration Due to Gravity
There are now two ways to calculate gravitational force on an object:

4. Acceleration Due to Gravity
There are now two ways to calculate gravitational force on an object:

5. Acceleration Due to Gravity
There are now two ways to calculate gravitational force on an object:

6. Acceleration Due to Gravity
There are now two ways to calculate gravitational force on an object:

7. Acceleration Due to Gravity
There are now two ways to calculate gravitational force on an object:

8. Acceleration Due to Gravity

9. Using the equation for acceleration due to gravity, we discover an amazing result!
g = 9.8 m/s2
Radius of Earth is x 106 meters

10. Example 2
What does an 80.0 kg astronaut weigh on the Moon? Mass of Moon = 9.35 x 1022 kg
Radius of Moon = x 106 m

12. Calculate the acceleration due to gravity on the Moon’s surface
Calculate the acceleration due to gravity on the Moon’s surface. Mass of Moon = 9.35 x 1022 kg
Radius of Moon = x 106 m
Example 3

13. Is there no gravity on the space station?
wk7PXg

14. To us, weight is a feeling. Not to a physicist!

15. Weight and Gravity in Physics
In physics, weight is a measure of the gravitational force acting on an object.
To be “weightless” in our mind is to have nothing stopping us from accelerating due to gravity.
This is not truly weightlessness—in fact, to accelerate means to experience a gravitational force and thus have a weight!
So, even if you are in free fall and feel weightless, gravity still acts on you and you have weight because of that fact alone.

16. So, is there no gravity on the space station?
The space station and its contents obviously experience a gravitational force from the Earth because it is orbiting the Earth!
The space station actually is “falling” around the Earth, so it is in free fall.
The astronauts inside feel weightless because they are in free fall, but we know that gravity is still acting on them.

17. Acceleration Due to Gravity Practice
Weight for it…