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14. waves and sound — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
In Melde's experiment, the string vibrates in $4$ loops when a $50 \,gram$ weight is placed in the pan of weight $15\, gram.$ To make the string to vibrates in $6$ loops the weight that has to be removed from the pan is
  • A
    $0.0007\, kg\, wt$
  • B
    $0.0021\, kg\, wt$
  • ✓
    $0.036 \,kg \,wt$
  • D
    $0.0029 \,kg \,wt$
✓

Answer

Correct option: C.
$0.036 \,kg \,wt$
c
(c) Frequency of vibration of string is given by 

$n = \frac{p}{{2l}}\sqrt {\frac{T}{m}} $==> $p\sqrt T = $constant ==> $\frac{{{p_1}}}{{{p_2}}} = \sqrt {\frac{{{T_2}}}{{{T_1}}}} $ 

Hence $\frac{4}{6} = \sqrt {\frac{{{T_2}}}{{(50 + 15)gm{\rm{ - }}force}}} $==> ${T_2} = 28.8\,gm{\rm{ - }}f$ 

Hence weight removed from the pan

$ = {T_1} - {T_2} = 65 - 28.8 = 3.62\,gm-force = 0.036 kg-f.$

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