Question

You watch a distant lady driving nails into her front porch at a regular rate of 2 strokes per second. You hear the sound of the blows exactly synchronized with the blows you see. And then you hear one more blow after you see her stop hammering. How far away is she? The speed of sound is 340 m/s.

Answer 1

Since the lady is capable of delivering 2 strokes in 1 second, we know that it takes 0.5 seconds for one stroke of the hammer.

It is given that one more blow is heard even after she is seen as stopping hammering. This means that the sound from the last blow reached us a little later: 0.5 seconds after the last blow.

So, we know that time taken for the sound from the last blow to reach us t = 0.5 s

Speed of Sound is given as V = 340 m/s

Distance of the lady from us D = ?

Using the equation D = V.t, we get D = (340)(0.5) = 170 m

Thus, we can understand that the lady is 170 meters away from us.