# Homework Help: What is the speed of water waves?

1. Jan 30, 2005

### jai6638

Water waves in a shallow dish are 6 cm long. At one point, the water oscillates up and down at a rate of 4.8 oscillations per second.

A. what is the speed of water waves?

Do i have to just use the formula V=(lambda)(f) = (.06)(4.8) ??

thanks

Last edited: Jan 30, 2005
2. Jan 30, 2005

### Staff: Mentor

That's all there is to it. (Don't forget units.)

3. Jan 30, 2005

### jai6638

great thanks.. had another question:

Water waves in a lake travel 4.4 m in 1.8 s. THe period of oscillation is 1.2s.

A. What is the speed of water waves?
b. what is their wavelenght?

Answer A: v=(lambda) / (time)

what would i use as time here? 1.8 s or 1.2 s? why?

thanks

4. Jan 30, 2005

### jai6638

also , a sound wave of wavelength .70m and velocity 330m/s is produced for .50s.

A. How many complete waves are emitted in this time interval???
Do i have to calculuate frequency for this?

b. after .50s, how far is the front of the wave from the sourece of the sound?

wont it be .70m as its the wavelength?

thanks

5. Jan 30, 2005

### christinono

To answer these questions, you first have to calculate the speed of the wave using the simple formula v=dt. (use 4.4m and 1.8s)
To find the period, find the distance the wave travels in 1.2s (using the speed you calculated in A.)

6. Jan 30, 2005

### christinono

To answer A., you have to calculate the frequency.
To answer B., you cannot say the answer is .50s, since the question is not telling you it travels .70m in 0.50s. It is simply telling you that a wave HAVING a wavelength of .70m is "produced" for 0.50s. You just have to use the velocity (330m/s) and the time (0.50s) to calculate the distance it travels in 0.50s.

Always read the problem carefully before attempting to solve it.

7. Jan 30, 2005

### jai6638

so i get

V = (4.4)(1.8)= 7.92 m/sec
D = (1.2)(7.92) = 9.5 m
T = 9.5/ ( 1.2) (4.4 ) = 1.8 s !

damn .. im gettin the same T as in the question...?.. what am i doin wrong here

thanks ..

thanks

8. Jan 30, 2005

### jai6638

anyone?.....

9. Jan 30, 2005

### christinono

I don't quite get what you did...Don't you need to calculate the frequency first?

10. Jan 30, 2005

### jai6638

a) ok so finding the speed is simply the function of multiplying 4.4 and 1.8 right? ( since v = (lambda)(f) )

B) V = Lambda / Time

Lambda = (V) (time )
= (4.4)(1.8)(1.2)
= 9.5 m

is thta correct?

why would i need to find the frequency?

Last edited: Jan 30, 2005
11. Jan 30, 2005

### christinono

Which question are you talking about?
This one:
Water waves in a lake travel 4.4 m in 1.8 s. THe period of oscillation is 1.2s.

A. What is the speed of water waves?
b. what is their wavelenght?

or this one?:
also , a sound wave of wavelength .70m and velocity 330m/s is produced for .50s.

A. How many complete waves are emitted in this time interval???

12. Jan 30, 2005

### jai6638

talkinga bout :

Water waves in a lake travel 4.4 m in 1.8 s. THe period of oscillation is 1.2s.

A. What is the speed of water waves?
b. what is their wavelenght?

13. Jan 30, 2005

### christinono

OK. To find the speed, just use the formula d=vt (d=4.4 and t=1.8). To find the wavelength, just find the distance the wave travels in 1.2 seconds (using the same formula).

Nothing to it!

14. Jan 30, 2005

### jai6638

wow! that was stupid of me.... lol...

thanks much :)

15. Jan 30, 2005

### christinono

Physics has its way of seeming so hard at times... :tongue2:

16. Jan 31, 2005

### jai6638

lol.. so true :)

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