Question

The escape velocity from the Earth is $11km{s}^{-1}$. The escape velocity from a planet having twice the radius and same mean density as that of Earth is :

• A. $11km{s}^{-1}$
• B. $5.5km{s}^{-1}$
• C. $22km{s}^{-1}$
• D. $10km{s}^{-1}$

Answer 1

The correct option is C $22km{s}^{-1}$

Escape velocity

$v_e=\sqrt{\frac{2GM}{R}}=R\sqrt{\frac{8}{3}\pi Gp}$

$\therefore v_e\propto R$ if p = constant

Since, planet has double the radius in comparison to the Earth

$\therefore v_e=22km{s}^{-1}$