Peoples Physics Concepts

http://www.ck12.org Chapter 11. Wave Motion and Sound

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/1844

Example 1

You want to create a 4th harmonic standing wave standing wave of frequency 10 Hz on a rope. Prior to conducting

your experiment, you are able to create a 1st harmonic standing wave with the exact same kind of rope at the same

tension and you measure the frequency to be 3 Hz. What length of rope will you need to use in order to create your

4th harmonic standing wave at 10 Hz?

Solution

This is a two step problem. We’ll start by finding how fast waves travel along the rope using the information from

the prior test.

f 1 =

nv

2 L

v=

f 12 L

n

v=

3 Hz∗ 2 ∗1 m

1

v=6m/s

Now that we have the speed of waves on the rope, we can use that to find the length we need.

f 4 =

nv

2 L

L=

nv

2 f 4

L=

4 ∗6 m/s

2 ∗10 Hz

L= 1 .2 m

Watch this Explanation