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 minuteĀ
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