PASCO WA-9857, Инструкция по эксплуатации

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String Vibrator Standing Waves In Strings
20
®
2. For every value of mass, calculate the tension (including uncertainty) in the string.
Tension = F = mg
3. Make a graph of F versus n. Describe in words the shape of the graph.
4. For every value of n, calculate 1/n
2
. Make a graph of F versus 1/n
2
. Does the graph look
linear?
5. Find the slope (including uncertainty) of the best fit line through this data.
6. Combine equations 1, 2, and 3 (from the Theory section), and show that the tension can be
written as:
Thus the slope of an F versus 1/n
2
graph is 4
µ
f
2
L
2
.
7. Use the slope from your graph to calculate the density,
µ
, of the string. Also calculate the
uncertainty of
µ
.
8. Compare this measured value of density to the accepted value. (You calculated the accepted
value of
µ
from the mass and length of the string). What is the difference? How does the
difference to compare the uncertainty that you calculated in step 7?
9. Calculate the percent deviation of the measured value of
µ
from the accepted value of
µ
.
Further Investigations
1. Hang a mass on the string with a value that is about halfway between the masses that
produced standing waves of 3 and 4 segments. The string should show no particular mode.
Place a “bridge” so that you can see the exact fundamental (n = 1) between the String
Vibrator and the bride. What is the wavelength?
Slide the bridge away from String Vibrator until the string vibrates in 2 segments. How does
the wavelength of the two-segment wave compare to the wavelength of the previous one-
segment wave?
Why is a standing wave created only when the bridge is at certain locations? What are these
locations called?
2. If a strobe is available, observe the standing wave on a string with the strobe light. Draw a
diagram explaining the motion of the string.
F 4
µ
f
2
L
2
 
  1
n
2
-----
 
 
 
=
% Deviation
Measured Accepted –
Accepted
----------------------------------------------------
100%
×
=