Chapter 26, Problem 29A

You watch a distant farmer driving a stake into the ground with a sledgehammer. He hits the stake at a regular rate of one stroke 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 him stop hammering. How far away is the farmer?

To determine

To determine the distance of the farmer from a person who hear the sound made by the farmer.

Answer to Problem 29A

The farmer is 340 m away.

Explanation of Solution

Given Info:

Let the farmer is at a distance d from the person.

The delay in time between the blow seen and the sound heard is equal to the time taken by sound to reach the person.

Time taken by sound to travel a distance d is t = 1 s

The speed of sound at room temperature v = 340 m/s

Formula Used:

  $\begin{array}{l}\text{Distance travelled =}\left(\text{speed}\right)\left(\text{time}\right)\\ \text{d= v t}\end{array}$

Calculation:

Plug all the known quantities in the above equation $$

  $\begin{array}{l}\text{d=}\left(\text{340m/s}\right)\left(\text{1s}\right)\\ \text{d = 340 m}\end{array}$

Conclusion:

The farmer is at a distance 340 m away from a person observing his action.