A simple pendulum oscillating in air has period T . The bob of the pendulum is completely immersed in a non-viscous liquid. The density of the liquid…
JEE Main 2019 — Physics Waves & Oscillations
2019mcqhard
A simple pendulum oscillating in air has period T . The bob of the pendulum is completely immersed in a non-viscous liquid. The density of the liquid is 161th of the material of the bob. If the bob is inside liquid all the time, its period of oscillation in this liquid is:
Official previous-year question
Held on 9 Apr 2019 · Verified 6 Jul 2026.
Options
A
2T101
B
2T141
C
4T151
D
4T141
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Solution
Let the density of bob is σ & density of liquid is 16σ .
Now, Net downward force on bob = Weight - Buoyancy
=σVg−16σVg=1615σVg
Net effective gravitational acceleration =σV1615σVg=1615g
Time period (T)=2πgeffl=2π1615gl=2π1516gl=1516⋅(2πgl)=154T
=4T151
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