# A hiker shouts toward a vertical cliff 685 m away. The echo is heard 4.00 s later. What is the speed of sound in air?

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The wavelength of the sound is 0.750 m. What is its frequency? What is the period of the wave?

The wavelength of the sound is 0.750 m. What is its frequency? What is the period of the wave?

##### 2 Answers

#### Answer:

The speed is 342.5 metres per second.

#### Explanation:

The sound has to travel to the cliff and back again. So the sound travels

This takes 4.00 seconds

So applying the concept of ratio

Let

By ratio:

Thus we need to find a way to convert 4 into 1 so that the left side of the = is the same as the right side.

To maintain the ratio of a fraction : what yo do to the top of a fraction you also do to the bottom.

So the speed is 342.5 metres per second.

#### Answer:

I found

#### Explanation:

The sound has to travel twice the distance to go and come back to be heard:

Speed is