A) 5 s
B) 0.36 s
C) 5.36 s
D) 2 s
Correct Answer: C
Solution :
Initial velocity, u = 0 (body at rest) Let \[{{t}_{1}}\] be the time taken by the stone to reach the pond. For a freely falling body \[h=ut+\frac{1}{2}g{{t}^{2}}\Rightarrow 125=0\times {{t}_{1}}+\frac{1}{2}10\times t_{1}^{2}\] \[t_{1}^{2}=25\Rightarrow {{t}_{1}}=5s\] Let the time taken by sound to reach the top \[={{t}_{2}}\] Speed\[\text{=}\frac{\text{Distance}}{\text{Time}}\text{ or 340=}\frac{125}{{{t}_{2}}}\] \[{{t}_{2}}=\frac{125}{340}=0.36s\] Time after which splash will be heard at the top \[={{t}_{1}}+{{t}_{2}}=5+0.36=5.36s\]
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