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Question: Answered & Verified by Expert

A particle of mass m is moving in time t on a trajectory given by, 

r=10αt2i^+5βt-5j^

where α and β are dimensional constants.

The angular momentum of the particle becomes the same as it was for t=0 at time t=_____ seconds.

PhysicsRotational MotionJEE MainJEE Main 2021 (25 Jul Shift 1)
Solution:
1267 Upvotes Verified Answer
The correct answer is: 10

r=10αt2i^+5βt-5j^

v=20α+i^+5βj^

L=mr×v

=m10αt2i^+5βt-5j^×20αi^+5βj^

L=m50αβt2k^-100αβt2-5tk^

At t=0, L=0

50αβt2-100αβt2-5t=0

t-2t-5=0

t=10 sec

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