The escape speed from planet x is 20,000 m/s. planet y has the same radius as planet x but is twice as dense. what is the escape speed from planet y?

the escape speed from planet Y is times the escape speed from planet X.

Explanation:

The escape speed from a surface of a planet is given by:

where

G is the gravitational constant

M is the mass of the planet

R is the radius of the planet

Let's call M the mass of planet X and R its radius. So the speed

corresponds to the escape speed from planet X.

Now we now that planet Y has:

- same radius of planet X: R' = R

- twice the density of planet X: d' = 2d

The mass of planet Y is given by

where V' is the volume of the planet. However, since the two planets have same radius, they also have same volume, so we can write

which means that planet Y has twice the mass of planet X. So, the escape speed of planet Y is

so, the escape speed from planet Y is times the escape speed from planet X.