Physics 9702 · AS & A Level · Gravitational force between point masses
Gravitational force between point masses — practice question
A moon travels in a circular path of radius $r$ around a planet. The moon’s angular speed in this orbit is $\omega$. The planet and its moon can be treated as isolated point masses in space.
(a)[3]
Show that the relationship between $r$ and $\omega$ is $r^3\omega^2 = \text{constant}$. Give working to support your answer.
(b)
(b(i)(1))[3]
Use the values in Fig. 1.1 to work out the mass of Mars.
(b(i)(2))[3]
Use the data in Fig. 1.1 to find the orbital period of Deimos around Mars.
(b(ii))[1]
Mars rotates about its axis in $24.6$ hours. Deimos follows an equatorial orbit and moves in the same direction as Mars spins about its axis. Use your answer in (i) to comment on the orbit of Deimos.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The gravitational force supplies the centripetal force” …