One can set up standing waves on a string which is fixed at both ends by vibrating it at just the right frequency. At the right frequency, waves travelling down the string will interfere constructively with each other and with waves travelling in the opposite direction.
In fact, there are a whole set of frequencies which will work: a fundamental frequency f1 and its harmonics, 2*f1, 3*f1, , etc. As shown in this week's lab manual, the fundamental frequency is given by
1 F frequency f1 = --- * sqrt (--------) 2*L muwhere
f1 is the fundamental frequency (Hertz, or 1/s) L is the length of the string (meters) F is the force of tension on the string (Newtons) mu is the linear mass density of the string (kg/meter)
This week, you will set up standing waves at a set of frequencies, and use the above equation to figure out what the linear mass density of the string ought to be. Then, you'll compare it to the actual linear mass density, and see if the theory actually works.
Your job this week:
At this point, you should come to me and tell me what the linear mass density of the unstretched string is -- with uncertainty, of course. I'll write it down in my little black book. Then, you may use the Meittler balance to measure directly the mass of a length of unstretched string, from which you can calculate the real linear mass density.
Answer the questions:
You may NOT use a computer for any purpose in this week's exercise. Paper, pencil, ruler, calculator -- no more.
Once again, I want to try to give you a chance to finish all your work by the end of the lab period. Therefore, I expect:
I will deduct a full letter grade from any report which includes the phrase "human error."
Last modified Apr 11, 2001 by MWR.
Copyright © Michael Richmond. This work is licensed under a Creative Commons License.