Physics

Problem

Two spherical planets

P

and

Q

have the same uniform density. The radius of

Q

is twice that of

P

. If the escape velocity at the surface of

P

10\,\text{km s}^{-1}

, what is the orbital speed of a satellite moving just above the surface of

Q

? a)

20\,\text{km s}^{-1}

7.1\,\text{km s}^{-1}

14\,\text{km s}^{-1}

10\,\text{km s}^{-1}