### Q.2:- A stone dropped from the top of a tower of height 300 m high splashes into the water of a pond near the base of the tower. When is the splash heard at the top given that the speed of sound in air is 340 m s^{–1}? (g= 9.8 m s^{–2})

**Answer:-**

Height of the tower, *s* = 300 m

Initial velocity of the stone, *u* = 0

Acceleration, *a* = *g* = 9.8 m/s^{2}

Speed of sound in air = 340 m/s

The time (*t*_{1}) taken by the stone to strike the water in the pond can be calculated using the second equation of motion, as:

*s* = *ut*_{1} + 1/2 *gt*_{1}^{2}

300 = 0 + 1/2 × 9.8 × *t*_{1}^{2}

∴ *t*_{1} = √300 × 2/9.8 = 7.82 s

Time taken by the sound to reach the top of the tower, *t*_{2} = 300/340 = 0.88 s

Therefore, the time after which splash is heard, *t* =* t*_{1} + *t*_{2}

= 7.82 + 0.88 = 8.7 s.