2.00E+08
2.50E+08
3.00E+08
3.50E+08
4.00E+08
f(x) = 287527461001.53x - 36951537.42
Stress vs Strain Graph 2
Strain
Stress (N/m)
F = mg = (1 kg)*(9.8m/s
2
) = 9.80 N
ΔL = L
2
– L
1
= 7.61 mm – 7.42 mm = .19 mm

Strain = ΔL / L = .19 mm / 680 mm = 2.79 x 10
-4
Stress = F / A = 9.80 N / 2.12 x 10
-7
m
2
= 4.62 x 10
7
Discussion:
1.
When the elastic limit is not exceeded, the deformation is recoverable so comparing both cases of
increasing and decreasing the hanging weights, the strain should be the same for the same stress.
That is the Young’s Modulus should be the same for both cases. Do you observe this?
a.
Yes, when you increase and decrease the weights, Young’s Modulus remains the same for
both cases. When you look at the graphs, you can see that they are inverses of each other.
2.
In your plot, how well the data point falls in a straight line? What would be the factors that cause
the deviation from the straight line?
a.
The points did not fall in a perfectly straight line. This error could have been caused
because of human error and/ or because of equipment not being accurate or calibrated.
3.
If the wire in your apparatus is replaced with one twice as thick, which of the following would
change when you add the first kilogram, and how: ΔL, F, stress, strain, and value of Young’s
Modulus?
a.
If the wire is replaced with one that is two times as thick, stress would be half as much as
it is originally. The new value of Young’s Modulus would also be half its original value
because stress and area are inversely proportional. Also, because you would be dividing
double the amount you were before. In total: stress, strain, and Young’s Modulus would
all change.
4.
Does is make any significant difference whether you measure the diameter and the length of the
wire at the beginning (with only 1 kg), or when there are 7 kg total loaded on the hook?
a.
Yes, it does matter because the added weight on the wire could cause it to stretch. The
wire could also decrease in diameter if enough weight is added due the wire being
stretched and pulled.
Conclusion:
In conclusion, we learned how to find Young’s Modulus. We were able to get it by graphing stress vs strain
and finding the slope. We also learned that stress and strain are proportional to each other during this
experiment.

#### You've reached the end of your free preview.

Want to read all 5 pages?

- Spring '17
- HalinaOprychal
- Physics