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Orbital motionEdexcel A-Level Physics: Flashcards

What these 12 flashcards ask

  • What provides the centripetal force on a satellite in orbit?
  • Write the equation that equates gravity and centripetal force for a circular orbit.
  • Give the equation for orbital speed.
  • Does orbital speed depend on the mass of the satellite?
  • What happens to the orbital speed as the orbital radius increases?
  • Give the equation relating orbital period and radius.
  • What does T² ∝ r³ mean?
  • If the orbital radius is multiplied by 4, what happens to the period?
  • State the conditions for a geostationary orbit.
  • What is the orbital radius of a geostationary satellite around the Earth?
  • How can the mass of a planet be found from an orbiting moon?
  • Why do astronauts in orbit appear weightless?

Exam questions on Orbital motion

  1. An Earth-observation satellite moves in a circular orbit at a height of 600 km above the surface of the Earth. The mass of the Earth is 5.97×10²⁴ kg, its radius is 6.37×10⁶ m and the gravitational constant is G = 6.67×10⁻¹¹ N m² kg⁻².
    Calculate the orbital speed of the satellite.2 marks
  2. A television company uses a communications satellite that is placed in a geostationary orbit above the Earth. The mass of the Earth is 5.97×10²⁴ kg, its radius is 6.37×10⁶ m and the gravitational constant is G = 6.67×10⁻¹¹ N m² kg⁻². One day is 8.64×10⁴ s.
    Calculate the orbital radius of the satellite.2 marks
  3. The Moon orbits the Earth in an approximately circular path of radius 3.84×10⁸ m. Its orbital period is 27.3 days. Take G = 6.67×10⁻¹¹ N m² kg⁻².
    Use the motion of the Moon to calculate the mass of the Earth.3 marks
See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).