Lesson 12.3.1

12.3.1 Orbits under gravity Quiz: Pearson Edexcel Physics, Unit 12

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 12.3.1, Orbits under gravity: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 12: Gravitational Fields, written with Revision Ninja.

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The 20 questions

  1. What force provides the centripetal acceleration keeping a satellite in a circular orbit around Earth?

    • Electrostatic force
    • Gravitational force
    • Frictional force
    • Magnetic force

  2. Which expression gives the orbital speed v of a satellite at radius r about a mass M?

    • v = sqrt(G M r)
    • v = G M r^2
    • v = sqrt(G M / r)
    • v = G M / r

  3. What is the period of a geostationary satellite?

    • 12 hours
    • 24 hours
    • 365 days
    • 1 hour

  4. What is the relationship between orbital period T and radius r for a satellite about a planet?

    • T is proportional to r
    • T is proportional to 1/r
    • T^2 is proportional to r
    • T^2 is proportional to r^3

  5. Why do astronauts inside an orbiting space station experience apparent weightlessness?

    • Atmospheric drag acts
    • In free fall
    • Zero gravitational field
    • Centrifugal force balances

  6. A satellite orbits at radius 7.0 x 10^6 m about a planet with GM = 4.0 x 10^14 m^3 s^-2. What is its orbital speed?

    • 2.6 x 10^2 m s^-1
    • 1.1 x 10^4 m s^-1
    • 5.4 x 10^3 m s^-1
    • 7.6 x 10^3 m s^-1

  7. Using the satellite in the previous calculation (radius 7.0 x 10^6 m, speed about 7.6 x 10^3 m s^-1), what is its orbital period?

    • about 2.9 x 10^3 s
    • about 1.6 x 10^3 s
    • about 5.8 x 10^3 s
    • about 9.3 x 10^4 s

  8. A geostationary satellite has period 86400 s. Using GM = 4.0 x 10^14 m^3 s^-2, what is its orbital radius?

    • 1.7 x 10^5 m
    • 4.2 x 10^7 m
    • 3.6 x 10^8 m
    • 6.4 x 10^6 m

  9. If the orbital radius of a satellite is doubled, by what factor does its period change?

    • 4
    • about 2.8
    • 2
    • 8

  10. If the orbital radius of a satellite is doubled, by what factor does its orbital speed change?

    • 0.5
    • 1.41
    • about 0.71
    • 2.0

  11. The Moon orbits Earth at radius 3.8 x 10^8 m with period 2.4 x 10^6 s (about 27 days). Estimate Earth's mass using G = 6.67 x 10^-11 N m^2 kg^-2.

    • about 5.8 x 10^24 kg
    • about 2.0 x 10^30 kg
    • about 7.3 x 10^22 kg
    • about 6.0 x 10^22 kg

  12. How does the orbital speed of a satellite in a lower circular orbit compare to a higher orbit?

    • It is zero
    • It is slower
    • It is identical
    • It is faster

  13. What causes a low Earth orbit satellite to gradually lose orbital height over time?

    • Magnetic drag
    • Atmospheric drag
    • Increasing gravity
    • Solar radiation

  14. What happens to the kinetic energy of a satellite if its circular orbital radius is doubled?

    • It quarters
    • It quadruples
    • It halves
    • It doubles

  15. Two satellites have orbital radii r and 4r about the same planet, with equal masses. What is the ratio of the gravitational forces on them?

    • 1/4
    • 1/16
    • 1/2
    • 1/8

  16. What is the orbital period of a geostationary satellite orbiting Earth?

    • 90 minutes
    • 24 hours
    • 12 hours
    • 365 days

  17. Why is required orbital speed independent of the satellite mass?

    • Mass equals zero
    • Satellite mass cancels
    • Radius equals mass
    • Gravity is constant

  18. Which quantity of an orbiting satellite depends only on the central mass and orbital radius?

    • Kinetic energy
    • Orbital speed
    • Gravitational force
    • Total energy

  19. A satellite orbits at radius 4.0 x 10^7 m about a planet with GM = 4.0 x 10^14 m^3 s^-2. What is its orbital speed?

    • 1.0 x 10^4 m s^-1
    • 3.2 x 10^3 m s^-1
    • 1.6 x 10^3 m s^-1
    • 6.3 x 10^3 m s^-1

  20. Satellite A has an orbital period twice that of satellite B about the same planet. What is the ratio r_A / r_B of their orbital radii?

    • 2.0
    • about 1.6
    • about 4.0
    • 0.5

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