JEE Main 2023 · 12 April · morning · Single correct · +4 / −1
The ratio of escape velocity of a planet to the escape velocity of earth will be:-
Given: Mass of the planet is 16 times mass of earth and radius of the planet is 4 times the radius of earth.
- (a) 1: 4
- (b) 1: √2
- (c) 4: 1
- (d) 2: 1
Answer and solution
Answer (d) 2: 1
Solution
Physics sir · 3 steps
Escape velocity goes as the square root of M over R, so take the ratio and let G cancel.
- Escape velocity formula. For a planet of mass M and radius R, the escape velocity from its surface is vₑ = √(2GM/R). Only M and R change from planet to planet.
vₚ/vₑ = √(Mₚ/Mₑ×Rₑ/Rₚ)
- Put in numbers. Mₚ/Mₑ = 16 and Rₑ/Rₚ = 1/4. So vₚ/vₑ = √(16 × 1/4) = √4 = 2.
- So. The planet's escape velocity is twice the earth's, a ratio of 2 : 1, which is option (d).
The idea to keep. Escape velocity depends on √(M/R). Form the ratio first, cancel 2G, and do not forget the square root at the end.
Answer from the NTA final answer key. Solution by PrepWiser.