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- Oscillations
NEET · Physics · Oscillations
A simple pendulum is suspended from the celling of a lift. Three...
A simple pendulum is suspended from the celling of a lift. Three cases of lift are given
In which case time period of pendulum is (\mathrm{T}=2 \pi \sqrt{\frac{\ell}{\mathrm{~g}}})
In which case time period of pendulum is (\mathrm{T}=2 \pi \sqrt{\frac{\ell}{\mathrm{~g}}})
Options
- Aonly in (a)
- Bonly in (b)
- Conly in (c)
- Din both (a) & (b)
Correct answer
D. in both (a) & (b)
Step-by-step solution
(a) Lift is at rest (\mathrm{a}=0)
(b) lift is moving downward with constant speed
(\Rightarrow \quad) constant velocity (\Rightarrow \mathrm{a}=0)
in both cases (\mathrm{a}=0) so (\mathrm{g}_{\text{eff }}=\mathrm{g})
(\mathrm{T}=2 \pi \sqrt{\frac{\ell}{\mathrm{ g}}})
(c) In this case lift is moving with increasing speed so acceleration is downward.
(\mathrm{g}_{\mathrm{eff}}=\mathrm{g}-\mathrm{a})