1. The distance between two wave crests in the water is 3 meters. A swimmer notices one wave goes by every six seconds. What is the speed of the wave.

 

2. There is a delay of 5 seconds between the time you see a flash of lightning and hear the thunder. If the temperature is 20 degrees C, how far away is the lightning strike.

 

I haven't a clue where to start on either of these.

for the first one, use [math]v={\lambda}f[/math] where [math]{\lambda}[/math] is the wavelength and f is the frequency. also, T^-1=f where T is the period.

 

 

for the second, you'll need the formula for the speed of sound, but i don't know it off the top of my head.

Well, I got the first one and for the second one, I came up with the speed of sound being 349.16 m/s +/- 0.1

 

But after that, I'm not quite sure what to do.

Well, you have a time, and a velocity and want a distance... The time taken by the lightening to get to you can be pretty much disregarded as it'll be tiny...

1) speed (m/s) = wavelength x frequency

so . . .

(3m) x (how many waves in 1 second - oh - you've work it out)

 

2) speed of sound (m/s) x 5 seconds = distance (m)

 

Simple eh?