# Question 1. A deep well has water at a depth of 80m below the top of the well. A stone is dropped from the top. If the speed of sound is 320m/ s then the sound hitting the water is heard after how many seconds later?

Total distance travelled by the stone = 80m

Total distance travelled by sound = 80m= 160m

Time taken by stone to reach the well

$t_1=\sqrt{\frac{2s}{g}}=\sqrt{\frac{160}{10}}=4sec$

Time taken by sound to reach the top

$t_2=\frac{80}{320}=0.25sec$

Total time taken to hear the sound

$t=t_1+t_2=4+0.25=4.25sec$

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