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Question: Answered & Verified by Expert
After a perfectly inelastic collision between two identical particles moving with the same speed in different directions, the speed of the particles becomes half the initial speed. The angle between the velocities of the particles before the collision is
PhysicsCenter of Mass Momentum and CollisionJEE Main
Options:
  • A 60°
  • B 45°
  • C 120°
  • D 30°
Solution:
1679 Upvotes Verified Answer
The correct answer is: 120°
In a perfectly inelastic collision between two particles, linear momentum is conserved. Let θ  be the angle between the velocities of the two particles before the collision. Then

p2=p12+p22+2p1p2cosθ

or 2mv22=mv2+mv2+2mvmvcosθ

or  1 = 1 + 1 + 2 cos θ

or  cos θ = - 1 2

or θ=120°

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