Oscillations Ques 63

63. A mass $m$ is suspended from a two coupled springs, connected in series. The force constant for springs are $k_1$ and $k_2$. The time period of the suspended mass will be

[1990]

(a) $T=2 \pi \sqrt{\frac{m}{k_1-k_2}}$

(b) $T=2 \pi \sqrt{\frac{m k_1 k_2}{k_1+k_2}}$

(c) $T=2 \pi \sqrt{\frac{m}{k_1+k_2}}$

(d) $T=2 \pi \sqrt{\frac{m(k_1+k_2)}{k_1 k_2}}$

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Answer:

Correct Answer: 63.(d)

Solution:

  1. (d) The effective spring constant of two springs in series; $K=\frac{k_1 k_2}{k_1+k_2}$.

Time period,

$T=2 \pi \sqrt{\frac{m}{K}}=2 \pi \sqrt{\frac{m(k_1+k_2)}{k_1 k_2}}$