A) 25
B) 30
C) 35
D) 21
Correct Answer: D
Solution :
Key Idea: Pendulum having greater time period makes one oscillation less than the other. Time period of pendulum X is 4 s. Time period of pendulum Y is 4.2 s. If X makes n oscillation, then Y makes \[(n-1)\] oscillations. Time taken by X to make n oscillation \[=4n\] ...(i) Similarly, time taken by Y to make \[(n-1)\] oscillations \[=4.2(n-1)\] ?(ii) Equating Eqs. (i) and (ii), we get \[4.2n-4.2=4n\] \[\Rightarrow \]\[4.2n-4n=4.2\] \[\Rightarrow \]\[0.2\,n=4.2\] \[\Rightarrow \]\[n=\frac{4.2}{0.2}\] \[\therefore \] \[n=21\]You need to login to perform this action.
You will be redirected in
3 sec