Universe

Question 1

Why does your weight vary across planets?

Answer 1

● Your weight is dependant on g, since weight =
mass x g
● The gravitational field strength (g) of a planet
varies depending on the size of the planet
● This means that your weight will also vary

Question 2

What is gravitational field strength on Earth?

Answer 2

Approximately 10 N/kg

Question 3

What does our solar system consist of?

Answer 3

● The sun (our star)
● 8 Planets (Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus, and
Neptune)
● The planet’s natural satellites (ie. the moon)
● Dwarf planets
● Comets and asteroids

Question 4

Name the planets in order, starting with the closest

to the sun.

Answer 4

Mercury, Venus, Earth, Mars, Jupiter, Saturn,

Uranus, and Neptune

Question 5

What did Ptolemy suggest about the universe?

Answer 5

Geo-centric model (that the earth was at the centre)

Question 6

What did Copernicus suggest about the

universe?

Answer 6

Helio-centric model (That the sun is at the centre and the

planets orbit it)

Question 7

What did Galileo contribute to theories about the

universe?

Answer 7

He used telescopes to support
Copernicus’ suggestions about the
sun, and suggested that moons orbit
planets.

Question 8

Describe the orbits of moons, planets, comets and

artificial satellites.

Answer 8

They orbit in an elliptical shape

Question 9

Explain why for a stable orbit, the radius of orbit

must change if the speed changes

Answer 9

● At higher speeds, the object requires a greater
centripetal force
● For a greater centripetal force, the
gravitational force must increase
● This is achieved by the radius of the orbit
being reduced

Question 10

Explain how the force of gravity acting on a satellite

affects its speed and velocity

Answer 10

● The force can alter its velocity since the
direction is continually changing
● It can’t cause a change of speed since
there is no force component in the direction
of motion