Gravitational fields and Newton's law of gravitationEdexcel International A Level Physics: Mind map

Exam questions on Gravitational fields and Newton's law of gravitation

1. Treat the Earth as a uniform sphere of mass 5.97 × 10²⁴ kg and radius 6.37 × 10⁶ m. A communications satellite of mass 450 kg is 3.59 × 10⁷ m above the Earth's surface. The gravitational constant G = 6.67 × 10⁻¹¹ N m² kg⁻².
   Calculate the gravitational potential at the position of the satellite.2 marks
2. The Earth has mass 5.97 × 10²⁴ kg and the Moon has mass 7.35 × 10²² kg. The distance between their centres is 3.84 × 10⁸ m. Treat both as point masses at their centres. G = 6.67 × 10⁻¹¹ N m² kg⁻².
   Calculate the gravitational field strength of the Moon at the centre of the Earth, and state its direction.2 marks
3. In a hydrogen atom an electron and a proton are separated by 5.3 × 10⁻¹¹ m. The electron has mass 9.11 × 10⁻³¹ kg and the proton has mass 1.67 × 10⁻²⁷ kg. Each has a charge of magnitude 1.60 × 10⁻¹⁹ C. G = 6.67 × 10⁻¹¹ N m² kg⁻² and the constant in Coulomb's law, k = 1/(4πε₀), is 8.99 × 10⁹ N m² C⁻².
   Calculate the gravitational force between the electron and the proton.3 marks