# What is the speed of the waves on the lake?

1. Sep 20, 2008

### Foxhound101

1. The problem statement, all variables and given/known data
While anchored in the middle of a lake, you count exactly three waves hitting your boat every 12.0 s. You raise anchor and start motoring slowly in the same direction the waves are going. When traveling at 1.50 m/s, you notice that exactly two waves are hitting the boat from behind every 12.0 s.

What is the speed of the waves on the lake?

2. Relevant equations
f+-=(1+-v0/v)f0

3. The attempt at a solution

I have messed up this kind of problem before, so there are many places for me to make mistakes.

3 waves 12 seconds
V= 1.5m/s
2 waves 12 seconds

T1 = 4s
T2 = 6s

f1=.25
f2=.17

.17=(1-v0/1.5).25

.68=1-v0
-.32=-v0/1.5
.48=v0

I know I made a mistake somewhere...

2. Sep 20, 2008

### Gear300

Re: Waves

You got the overall idea for the equations but you made a slight mistake...1.5 m/s is the value of Vo (the object's velocity) and v is the velocity of the wave. You mixed the two up.

3. Sep 20, 2008

### Foxhound101

Re: Waves

Thank you, that was the mistake.