Question

A stone is dropped from cliff into a lake 80 m deep. Another cliff which is 200 m away from the lake reflects the sound of splash . What is the time difference between the sounds of the first splash and echo of splash? Take speed of sound is 340 ms1 and g = 10 msal 3N​

Answer 1

Answer:

Correct option is

C

11.5 s

Height of the tower  S=500 m

Initial speed of the stone  u=0

Acceleration due to gravity acting on the stone  g=10m/s2

Using  S=ut1+21gt12

where t1 is the time taken by the stone to reach the lake.

∴  500=0+21(10)t12

We get  t1=10 s

Speed of sound in air  v=330m/s

Time taken by the sound of splash to reach the top of tower  t2=vS

∴  t2=330500=1.5 s

Thus total time after which the sound of splash will be heard  t=t1+t2

∴  t=10+1.5=11.5 s