Youngs modulus isnt coming out as constant

In summary, the Homework Equations state that stress is force divided by area and strain is extension divided by original length. For this particular homework, the Youngs Modulus is a constant and should be calculated using the two values of force and extension. It was found that the wire broke because it was stretched beyond its elastic limit and displayed plastic behavior. The graph of stress against strain was difficult to plot because it only showed over a linear elastic region. However, the Youngs Modulus can still be found by plotting the line of best fit close to the origin.
  • #1
smolly
5
0

Homework Statement


hey
my youngs modulus for all my results for c.w has come out "blehege"
Y=youngs modulus
F=force
A= area 5.255x10-8
X=extension
L= original length 1m make things quicker
my Y for when F=1.5 and X=0.05x10-3 i get a stress of 26198585 my stress is 2000 which makes my Y=5.2x10to the 10
and later on when my F=11 and X=10x10-3 my stress is 192122958 and stress 100 which makes Y= 1.9x10 to the 10
ive done something really wrong here but i can't figure it out...can someone take these results and make them so there right and give me there method ><


Homework Equations


i used
Stress = force divided by area
strain = extension divided by original length
Youngs modulus= stress divided by strain

on my results page of my c/w my teacher wrote that it should be a constant which makes sense so i think i worked something out wrong? or is it just my equipment was so bad its going to be miles off?
 
Physics news on Phys.org
  • #2
Haven't checked your maths but your equation is correct. It seems that you applied two forces only and calculated Y for each one.Y is a constant and you should have used your two values to calculate the average value.It would be better to use a range of forces and plot a graph of stress against strain.Y can be found from the gradient of the graph.
 
  • #3
i did do results for every 0.5N so 1, 1.5, 2 , 2.5 etc till my copper wire broke at 14N i just used those 2 results cause if its constant surely 1.5 should be roughly equal to 6.5?
i just thought of this? is youngs modulus a constant decrease? or should it be constantly the same?
 
  • #4
Since your wire broke you stretched it beyond its elastic limit and before breaking it started to display plastic behavior.Try the graph of stress against strain(or it may be easier to plot force and extension)and calculate Y from the linear part of your graph..It is only over this linear elastic region that Y is a constant.
 
  • #6
To measure youngs modulus accurately you need some quite sophisticated equipment and if you didnt have this your results will have large experimental errors.I think the best you can do is plot the line of best fit close to the origin.
 
  • #7
ok thanks! so can i basically say that my youngs modulus is abit skewif cause my equipment was really inaccurate?
was a 1M ruler and my eye site^^
 
  • #8
It's possible that it's experimental error, but try graphing it. You shouldn't get a simple linear relationship.
 
  • #9

Related to Youngs modulus isnt coming out as constant

1. What is Young's Modulus?

Young's Modulus, also known as the modulus of elasticity, is a measure of a material's stiffness or resistance to deformation. It is defined as the ratio of stress to strain within the elastic limit of a material.

2. Why might the value of Young's Modulus not be constant?

The value of Young's Modulus can vary due to a number of factors, such as temperature, pressure, and material composition. It can also vary depending on the direction in which the stress and strain are applied.

3. How is Young's Modulus typically measured?

Young's Modulus is typically measured using a tensile test, where a sample of the material is subjected to a controlled amount of stress until it reaches its elastic limit. The resulting strain is then measured and used to calculate the modulus.

4. Can Young's Modulus change over time?

In most cases, Young's Modulus is considered to be a constant value for a given material. However, it can change over time due to factors such as fatigue, creep, and material degradation.

5. How does Young's Modulus relate to a material's strength?

Young's Modulus is a measure of a material's stiffness, not its strength. The strength of a material is typically measured using its yield strength or ultimate tensile strength, which are different properties than Young's Modulus.

Similar threads

  • Introductory Physics Homework Help
Replies
4
Views
232
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
19
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
1K
Replies
23
Views
3K
  • Introductory Physics Homework Help
Replies
19
Views
2K
  • Introductory Physics Homework Help
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
9
Views
2K
Back
Top