# Homework Help: Harmonic oscillation

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1. Dec 3, 2015

### CMATT

(a) A wave traveling on a Slinky® that is stretched to 4.5 m takes 2.6 s to travel the length of the Slinky and back again. What is the speed of the wave?
For this one, I did v = d/t
= 4.5 m / 2.6 s
= 1.73 m/s

Then I did v = (1.73)(2) = 3.46 m/s
This is correct

(b) Using the same Slinky stretched to the same length, a standing wave is created which consists of 5 antinodes and 6 nodes including both ends. What is the wavelength of the wave?
I keep getting stuck on this one, and (c) below. I know this answer should be in meters.

(c) At what frequency must the Slinky be oscillating?
I know this answer should be in Hz.

Im not sure which equations to use for (b) and (c)

Any help is greatly appreciated!

2. Dec 3, 2015

### vela

Staff Emeritus
Not really. There's no good reason to divide 4.5 m by 2.6 s as those two quantities don't have anything to do with each other.

Start by drawing a picture of a snapshot of the standing wave. You can then identify what fraction of the length of the Slinky is equal to one wavelength.

3. Dec 3, 2015

### davenn

read the question again, do you see where you made a mistake in your assumption ?
Note particularly the length, total length and travel time

Dave

4. Dec 4, 2015

### J Hann

You need to identify the nodes and anti-nodes.
What is the distance between them?
A diagram would be useful in this regard.
The waves being referred to are probably compressional waves, so if you have studied sound waves which
travel by compressions and rarefactions, then how do these relate to wavelength.
Also, you know that if the Slinky is stretched to the same length then the tension in the Slinky is constant.
How does tension relate to frequency and wavelength?
Hope you find these comments useful.

5. Dec 4, 2015

### CMATT

Yes I made a diagram, it was very useful.
I figured it out! Thank you for your help

6. Dec 4, 2015

### CMATT

Thanks for your help Dave!