Planets X and Y are uniform spheres of the same density

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Planets X and Y are uniform spheres of the same density. The radius of X is twice the radius of Y. If

v_X

and

v_Y

are the escape velocities from their surfaces respectively, what is the ratio

v_X : v_Y

? (a)

\sqrt{2} : 1

(b)

2 : 1

(c)

1 : \sqrt{2}

(d)

4 : 1