Physics - Rotation Question with Solution | TestHub

PhysicsRotationAngular momentumHard2 minPYQ_2023
PhysicsHardinteger

A thin circular coin of mass 5 gm and radius 43 cm is initially in a horizontal xy-plane. The coin is tossed vertically up (+z direction) by applying an impulse of π2×10-2 N-s at a distance 23 cm from its center. The coin spins about its diameter and moves along the +z direction. By the time the coin reaches back to its initial position, it completes n rotations. The value of n is _____.

[Given: The acceleration due to gravity g=10 m s−2]

Answer:
30
Solution:

By impulse - momentum theorem:

J=MVCM

⇒ VCM=JM=π2100×51000=2π m s-1

⇒ Total time of journey =2VCMg=2g×2π

⇒ ∆t=2π5 s

Also, by angular impulse- momentum theorem:

J×R2=Iω⇒J×R2=MR24ω

⇒ ω=J×R2MR24=JMR×2

=π2100×251000×43×1100

=1502π rad s-1

⇒ Number of rotations =ω∆t2π

=1502π×2π52π=30

Therefore, n=30.

Stream:JEE_ADVSubject:PhysicsTopic:RotationSubtopic:Angular momentum
⏱ 2mℹ️ Source: PYQ_2023

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