Two planets have masses and and their radii are and

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

Problem

Two planets have masses

M

and

16M

and their radii are

a

and

2a

, respectively. The separation between the centres of the planets is

10a

. A body of mass

m

is fired from the surface of the larger planet towards the smaller planet along the line joining their centres. For the body to be able to reach the surface of smaller planet, the minimum firing speed needed is : [Main 6 Sep. 2020 (II)] (1)

2\sqrt{\frac{GM}{a}}

(2)

4\sqrt{\frac{GM}{a}}

(3)

\sqrt{\frac{GM^2}{ma}}

(4)

\frac{3}{2}\sqrt{\frac{5GM}{a}}

Related theory

Universal Law of Gravitation
Gravitation
Gravitational Potential Energy
Escape velocity
Gravitational potential and energy
Escape speed

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