Answer:
option ( a ) is correct .
Explanation:
Escape velocity on the earth = ā ( 2 GM / R )
where G is universal gravitational constant , M is mass of the earth and R is radius .
Vā = ā ( 2 GM / R )
escape velocity on the planet where mass is equal is earth's mass and radius is 4 times that of the earth
Radius of the planet = 4 R
escape velocity of planet = ā ( 2 GM / 4R )
= .5 x ā ( 2 GM / R )
= .5 Vā
option ( a ) is correct .
