Astrophysics - Motion in the Universe

Question 1

what is gravity?

Answer 1

a force that acts between all objects with mass

Question 2

What does gravitational field strength depend on?

Answer 2

• the mass of the object

- your distance from the object

Question 3

What is the gravitational field strength on earth?

Answer 3

9.8

Question 4

What is the gravitational field strength on the moon?

Answer 4

1.6

Question 5

What is the gravitational field strength on mars?

Answer 5

3.8

Question 6

What is the gravitational field strength on Jupiter

Answer 6

25

Question 7

What causes moons and artificial satellites to orbit planets?

Answer 7

the gravitational attraction of the planet pulls the moon/satellite to the planet

Question 8

What causes comets and planets to orbit the sun?

Answer 8

the gravitational attraction of the planet which pulls the planet/comet to the planet

Question 9

Similarities between comets, moons and planets

Answer 9

• their orbits are all slightly elliptical
• they all orbit in the same plane
• they all travel in the same direction around the sun

Question 10

Differences between comets, moons and planets

Answer 10

• they orbit at different distances and speeds

- they take different amounts of time to orbit the sun

Question 11

Comets

Answer 11

• the orbits of comets are highly elliptical

- this causes the speed of the comets to change significantly as its distance from the sun changes

Question 12

What happens to a comet as it approaches the sun?

Answer 12

• it loses gravitational potential energy and gains kinetic energy
• the comet speeds up
• the icy body of the comet starts to melt and forms a tail which always points away from the sun

Question 13

equation for orbital speed

Answer 13

orbital speed = 2π x orbital radius / time period

v = 2 x π x r / t