A girl stands 170 m away from a high wall and claps her hands at a steady rate so that each clap coincides with the echo of the one before. a) If she makes 60 claps in 1 minute, what value should be the speed of sound in air? b) Now, she moves to another location and finds that she should now make 45 claps in 1 minute to coincide with successive echoes. Calculate her distance for the new position from the wall.

After going through we can list some data as,

distance d = 170 m

To find a) speed v = ? 

             b) distance d= ?

Solution –

a)its given that girl makes 60 claps in one minute 

hence she makes 1 clap in 1 sec 

therefore we can say that 

in 1 sec the sound travel to the wall and comes back i.e it travels a distance equal to 2d means 340m 

hence speed v = distance / time 

v = 340/1 = 340m/s

b) now she is at some another location ,

let d be the distance between the girl and the wall 

now she makes 45 claps in 1 minute

i.e 45 claps in 60 sec

1 clap in 60/45 sec i.e 1.333 sec

hence we can say in 1.333 sec the sound travel to the wall and comes back i.e it travels a distance equal to 2d

distance = speed x time

2d = 340 x 1.333 = 453.22 m 

therefore d = 453.22/2 = 226.61 m