A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.
Correct Answer: C
Solution :
Frequency of second pendulum \[\nu =(1/2){{s}^{-1}}.\] When elevator is moving upwards with acceleration g/2, the effective acceleration due to gravity is \[g=g+a=g+g/2=3g/2.\] As \[\nu =\frac{1}{2\pi }\sqrt{\frac{g}{l}}\] so \[{{\nu }^{2}}\propto g.\] \ \[\frac{\nu _{1}^{2}}{{{\nu }^{2}}}=\frac{{{g}_{1}}}{g}=\frac{3g/2}{g}=\frac{3}{2}\]or, \[\frac{{{\nu }_{1}}}{\nu }=\sqrt{\frac{3}{2}}\]=1.225 or, \[{{\nu }_{1}}=1.225\nu =1.225\times (1/2)=0.612\ {{s}^{-1}}.\]
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