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Question: Answered & Verified by Expert
A particle of mass m is projected at an angle of 60o with a velocity of 20 m/s relative to the ground from a plank of same mass m which is placed on a smooth surface initially plank was at rest. The minimum length of the plank for which the ball will fall on the plank itself is

PhysicsMotion In Two DimensionsJEE Main
Options:
  • A 4 0 3  m
  • B 2 0 3  m
  • C 1 0 3  m
  • D 6 0 3  m
Solution:
1206 Upvotes Verified Answer
The correct answer is: 4 0 3  m




Since the external force on the system is zero, location of COM will not shift.

   m1x1=m2x2

m x=mL-x

   x=L2

so plank will shift by L2 towards left.

Now range R should be <_ L2

     L=2R

L=2 u2sin30g=40 3

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