# Wave Motion

1. Apr 8, 2009

### tommyhakinen

1. The problem statement, all variables and given/known data
Ocean waves traveling to the east at speed of 4 m/s. the distance between the crests is 20 m. With what frequency do the waves hit the front of a boat moving westward at a speed of 1 m/s?

2. The attempt at a solution
Does the speed of the wave is added or subtracted from the speed of boat?

2. Apr 8, 2009

### Hootenanny

Staff Emeritus
You're travelling down the road in a car at 30mph, your mate is following in his car and is also travelling at 30mph. What is his speed relative to you?

Now, imagine the same scenario, but this time your mate is driving towards you. Will his speed appear faster or slower to you?

3. Apr 8, 2009

### tommyhakinen

in that case, it does not seems to move for me. am i right?
I see.. so, the answer is faster. am i right?
thank you very much..

4. Apr 8, 2009

### Hootenanny

Staff Emeritus
Correct, so if something is moving towards you do you add or subtract the objects speed from yours?

5. Apr 8, 2009

### tommyhakinen

i would add it to my speed. so if let say i am not moving, and the object is moving towards me with 1 m/s, it's speed appears to be 1 m/s to me as i am not moving. right?

6. Apr 8, 2009

### Hootenanny

Staff Emeritus
Correct.

So if you are moving at 1m/s and the waves are travelling towards you at 4m/s, what is the waves' speed relative to you?

7. Apr 8, 2009

5m/s..

8. Apr 8, 2009

### Hootenanny

Staff Emeritus
Spot on