Astrophysics
4 marks · EasyThe table below shows some information about two planets in our solar system and a moon of one of the planets.
| Name | Average distance from Sun (×10^8 km) | Type | Orbital time period (Earth years/days) |
|---|---|---|---|
| Venus | 1.08 | Planet | 0.6 years |
| Earth | 1.50 | Planet | 1.0 year |
| Moon | - | Moon of Earth | 27.3 days |
State the unit used for the average distance of planets from the Sun in the table.
Explain why the Moon is called a 'natural satellite' and not a planet.
Which of the two planets in the table has a stronger gravitational attraction from the Sun? Explain your answer using information from the table.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) kilometre (km)
(b) It orbits a planet (Earth) and is not a planet itself / a moon is a natural (not artificial) satellite.
(c) Venus. It is closer to the Sun (smaller distance in the table), so gravitational attraction is stronger.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies 'kilometre (km)' as the unit.
B1 (b) · 1 mark · Correct explanation that the Moon orbits Earth and is not a planet, or is a natural satellite.
B1 (c) · 1 mark · Names Venus correctly.
B1 (c) · 1 mark · Scientific explanation relating to gravitational attraction and distance from Sun.
Worked solution
(a) The unit is kilometre (km), as shown by the column title 'Average distance from Sun (×10^8 km)'.
(b) The Moon is a natural satellite because it orbits a planet (Earth), not the Sun, and it is not a planet itself.
(c) Venus feels a stronger gravitational attraction from the Sun because it is closer (1.08×10^8 km) than Earth (1.50×10^8 km). Gravitational force increases as distance decreases.