A-LevelPhysicsGravitational fields9702/43 · Oct/Nov 2019 · Q18 Marks
(a) State Newton's law of gravitation. (b) A geostationary satellite orbits the Earth. The orbit of the satellite is circular and the period of the orbit is 24 hours.
- (a)State Newton's law of gravitation.[2]
- (b)(i)State two other features of this orbit. 1. 2.[2]
- (b)(ii)The radius of the orbit of the satellite is 4.23 x 10⁴ km. Determine a value for the mass of the Earth. Explain your working.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [B1] (a) force proportional to product of masses and inversely proportional to square of separation
- [B1] (a) idea of (gravitational) force between point masses
- [B1] (b)(i) above the equator
- [B1] (b)(i) from west to east
- [B1] (b)(ii) gravitational force provides/is the centripetal force
- [C1] (b)(ii) GM / r² = r (2π / Τ)²
- [C1] (b)(ii) (6.67 x 10⁻¹¹ × M) = {(4.23 × 10⁷)³ × 4π²} / (24 × 3600)²
- [A1] (b)(ii) M = 6.0 x 10²⁴ kg
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