# Wave movement

## Homework Statement

A hiker shouts toward a vertical cliff 735 m away. The echo is heard 4.00 s later.
(a) What is the speed of sound of the hiker's voice in air?
[] m/s
(b) The wavelength of the sound is 0.732 m. What is its frequency?
[] Hz
(c) What is the period of the wave?
[] ms

(taken from webassign)

## Homework Equations

I would have thought it was V=d/s, but it doesn't work that way with this wave problem. Do I need to know the speed of sound?

## The Attempt at a Solution

I took 735/4 but it told me it was the wrong answer. I'm pretty sure I could figure out the rest of the problem if I could find velocity, so any help with that?

While I'm at it though

## Homework Statement

Water waves in a shallow dish are 5.5 cm long. At one point, the water moves up and down at a rate of 5.5 oscillations per second.
(a) What is the speed of the water waves?
[] m/s
(b) What is the period of the water waves?
[] s

Similar to the last problem, but I'm really clueless for this one.

I have until midnight to get these problems finished, so quick help would be appreciated. I don't even need the answer necissarily, just a way of solving it. Thanks