The radius of a planet is twice the radius of earth. Both have almost equal average mass-densities. v_ p and v_ e are escape velocities of the planet and the earth, respectively, then

Step-by-step solution

The escape velocity of earth, v_ e = 2 G M_ e R_ e =R_ e 8 3 G _ e Similarly for a planet, v_ p =R _ p 8 3 G _ p v_ e v_ p = R_ e R_ p _ e _ n Here, R_ p =2 R_ e , _ e = _ p v_ e v_ p = 1 2 or v_ p =2 v_ e