NTA Abhyas JEE Main2020PhysicsGravitationPractice
The gravitational potential of two homogeneous spherical shells A and B, having the same surface mass density, at their respective centres are in the ratio 3 : 4 . If the two shells coalesce into single one such that the surface mass density remains the same, then the ratio of potential at an internal point of the new shell and A is equal to
Options
- A3 : 2
- B4 : 3
- C5 : 3
- D5 : 6
Correct answer
C. 5 : 3
Step-by-step solution
M A = σ 4 π R A 2 ,   M B = σ 4 π   R B 2 where σ is surface density V A = - G M A R A ,       V B = - G M B R B V A V B = M A M B R B R A = σ 4 π R A 2 σ 4 π R B 2 R B R A = R A R B Given V A V B = R A R B = 3 4 then R B = 4 3   R A For new shell of mass M and Radius R - V V A = R R A = R A 2 + R B 2 R A = 5 3