ASTRO 7N - Unit 1, Part 1: Gravity Lesson

Mars has about 1/10 the mass of Earth and about 1/2 the radius of Earth. What is Mars' surface gravity compared to Earth?

0.4 times that of Earth

Saturn has about 100 times the mass of Earth and about 10 times the radius. What is the surface gravity of Saturn compared to Earth?

1

Law of Universal Gravitation

Fg = G (m₁ m₂) / r²

Mars has a lower surface gravity than Earth (True/False)

True

As the mass of the planet increases, the jump height _________ by the same factor as the mass.

decreases

Let's keep the mass Earth's mass but change the radius to twice the radius of Earth (2 R). How high do you jump?

four times as high

Now we can change the mass to 0.25 M. If we do, how much higher are you jumping?

four times as high

What is the relationship between gravity, mass, and radius? ("∝" means "proportional to")

g ∝ m/r²

How high are you jumping at twice Earth's mass (2 M) compared to Earth's mass?

half as high

As the radius of the planet increases, the jump height _________ as the square of the radius.

increases

Now we can change the mass to 0.5 M. If we do, how much higher are you jumping than at one Earth mass?

twice as high

Since the jump height is half as high, what does that tell us about the gravity?

twice as much

The Moon has about 1/100 the mass of Earth and about 1/4 the radius. What is the surface gravity of the Moon compared to Earth?

16/100

Jupiter has about 300 times the mass of Earth and about 10 times the radius. What is the surface gravity of Jupiter compared to Earth?

3

Let's keep the mass Earth's mass but change the radius to three times the radius of Earth (3 R). How high do you jump?

nine times as high

Keep the mass at Earth's mass but change the radius to half the radius of Earth (0.5 R). How much higher do you jump?

one-quarter as high