(ii) the lift is travelling at a constant velocity upwards of 4 m s−1?
(iii) the lift is travelling up with uniform acceleration of 2 m s−2?
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7. Taking the radius of Mars to be approximately 3440 km, calculate Mars’s gravitational attraction on a mass that weighs 200 N on Earth. (Mass of Mars = 0.11 × mass of Earth)
8. The mass of the Sun is approximately 3.2 × 105 times the mass of the Earth. The Sun is approximately 400 times further from the Earth than the Moon is from the Earth. Calculate the ratio of attraction of the Sun on the Moon to that of the Earth on the Moon. (You may assume that the Sun–Moon distance is constant and equal to the Sun–Earth distance. Take the distance from the Earth to the Moon as 3.8 × 108 m.)
9. Explain why the acceleration due to gravity is not constant everywhere on Earth.
10. Calculate the acceleration due to gravity 10 km above the Earth’s surface.
11. By what factor has the acceleration due to gravity reduced when you are at a height equal to fi ve times the radius of the Earth above the Earth’s surface?
12. There is a point between the Earth and the Moon where there is zero gravitational attraction from either, as their forces cancel out. Calculate this distance from the Earth (distance from Earth to Moon = 3.8 × 108 m).
