Q. The earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of the earth. The escape velocity of a body from this platform is fvₑ, where vₑ is its escape velocity from the surface of the earth. The value of f is :
A) 2
B) 1/√2
C) 1/3
D) 1
Explanation
[Solution from source] Escape velocity from a point at distance r from the centre is √(2GM/r). The platform is at r = R + R = 2R, so the escape velocity is vₑ/√2 and f = 1/√2. Escape becomes easier, not harder, so f cannot exceed 1. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.