Question

The escape velocity from the Earth's surface is υ. The escape velocity from the surface of another planet having a radius, four times that of Earth and same mass density is:

(1) 4 υ

(2) υ

(3) 2 υ

(4) 3 υ

Answer 1

v_e= v

v_e ⁄ v_p =√(2gr_e ⁄ 2gr_p)

          =√(r_e ⁄ 4r_e)

v_p = 2v