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Question: Answered & Verified by Expert
An object is projected from the earth's surface with escape velocity at 30° with horizontal. What is the angle made by the velocity with horizontal when the object reaches a height 2R from the earth's surface? R is the radius of the earth. Horizontal can be considered as a line parallel to the tangent at the earth's surface just below the object.
PhysicsGravitationJEE Main
Options:
  • A 30°
  • B 45°
  • C 60°
  • D 15°
Solution:
1643 Upvotes Verified Answer
The correct answer is: 60°
-GMmR  +  12mx2GMR=-GMm3R+12mv12

  v1=2GM3R

By conservation of angular momentum:

m×2GMRcos30°×R=m×v1cosθ×3R

cosθ=12  θ=60°

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