Young's Modulus, Stress/Strain graph and Calculating Energy

In summary, the conversation is about calculating the absorbed energy for a 2 day and 28 day sample using a simple method of counting squares. The person encountered difficulties in getting the same answer as the answer scheme and questioned if their counting method was incorrect.
  • #1
trew
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Homework Statement
as below
Relevant Equations
as below
ym.JPG

ym2.JPG


For part (b), I counted the number of squares underneath the 2 day sample to be roughly 33 'whole' squares (the 5by5 tiny squares is 1 whole sqaure).

I then equated 33 whole square = 0.35 MJ to calculate 1 whole square to be 0.0106 MJ.

I then counted the number of whole squares underneath the 28 day sample to roughly be 30.5 so the total absorbed energy is (30.5)(0.0106)=0.323..MJ

And found the percentage reduction to be around 7.6%. But then answer scheme has it between 12% and 15%.

No matter how many times I count the squares I can't get close to their answer. What am I doing wrong?

I know I could estimate the area by using the area of trapezium and triangle rules but I want to get this simple method right first.
 
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  • #2
trew said:
counted the number of squares underneath the 2 day sample to be roughly 33 'whole' squares (the 5by5 tiny squares is 1 whole sqaure).
Seems a bit low. I get closer to 36.
 
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Likes trew

Related to Young's Modulus, Stress/Strain graph and Calculating Energy

1. What is Young's Modulus?

Young's Modulus, also known as the modulus of elasticity, is a measure of the stiffness or rigidity of a material. It is defined as the ratio of stress (force per unit area) to strain (change in length per unit length) in a material that is being subjected to tensile or compressive forces.

2. How is Young's Modulus represented on a stress/strain graph?

Young's Modulus is represented by the slope of the linear portion of the stress/strain graph. The steeper the slope, the higher the modulus of elasticity of the material.

3. What is the relationship between stress and strain?

Stress and strain are directly proportional to each other. This means that as stress is applied to a material, it will deform and experience a change in length known as strain. The ratio of stress to strain is the material's Young's Modulus.

4. How is energy calculated from a stress/strain graph?

The area under the stress/strain curve represents the amount of energy absorbed or released by a material during deformation. This area can be calculated by finding the integral of the curve, which gives the energy per unit volume of the material.

5. What factors can affect Young's Modulus?

The modulus of elasticity can be affected by various factors, including temperature, pressure, and the microstructure of the material. Additionally, different materials have different inherent stiffnesses, so Young's Modulus can vary greatly between different materials.

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