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Question: Answered & Verified by Expert
A cylindrical plastic bottle of negligible mass is filled with 310ml of water and left floating in a pond with still water. If pressed downward slightly and released, it starts performing simple harmonic motion at angular frequency ω. If the radius of the bottle is 2.5cm then ω is close to: ( density of water =103kg/m3)
PhysicsOscillationsJEE MainJEE Main 2019 (10 Jan Shift 2)
Options:
  • A 5.00 rad sec-1 
  • B 2.50 rad sec-1
  • C 7.9 rad sec-1 
  • D 3.75 rad sec-1
Solution:
2902 Upvotes Verified Answer
The correct answer is: 7.9 rad sec-1 
Let at equilibrium, y length of bottle is immerged in water:

So, mg=fbuo

mg=ρAyg ..... (1) [Equilibrium Condition]

Now it is further pushed by distance x

Frestoring=ρ[Ax+y)g-mg

mω2x=ρAxg+ρAyg-mg

ω=ρAgm=ρAgρV=πr2gV=7.9 rad/sec

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