Young's modulus: Stress, Strain and Force for a Steel Bar

In summary, the conversation discusses errors in calculating strain and force in a workout problem. The speaker suggests using algebraic methods or calculator storage buttons to avoid rounding errors. They also mention using the formula F = k delta L as an alternative method, but are unsure of the value for k.
  • #1
chriscarson
197
26
Homework Statement
Problem to find strain and force
Relevant Equations
F = A E delta L
L
As all attempts to get it right but without success this is one of the problems with my workout . Where i did wrong calculations ?
The questions got the answers in brackets.
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  • #2
It looks like your answers for the strain and force match the book answers. What's the problem?
 
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  • #3
I know that can be rounded or something but when they have different numbers I need to be sure
 
  • #4
chriscarson said:
I know that can be rounded or something but when they have different numbers I need to be sure
What’s different?
 
  • #5
20200219_162629-1-1.jpg
20200219_162618-1-1.jpg


Strain and force have different numbers you can see .
 
  • #6
This is just because of rounding errors. Either yourself or the author have prematurely truncated the results from previous steps.

This goes to show the benefit of working algebraically and only substituting in numerical values in the final line of working. The alternative is to use the STORE buttons on your calculator, which is much more fiddly...
 
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  • #7
etotheipi said:
This is just because of rounding errors. Either yourself or the author have prematurely truncated the results from previous steps.

This goes to show the benefit of working algebraically and only substituting in numerical values in the final line of working. The alternative is to use the STORE buttons on your calculator, which is much more fiddly...
The strain maybe close but the force is way out i think.
 
  • #8
When you multiplied the stress by the area to get the force, you must have made a mistake in arithmetic. When I use your calculated area, I get their force. When I divide the stress by Young's modulus to get the strain, I confirm your value of 0.00137.
 
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  • #9
Chestermiller said:
When you multiplied the stress by the area to get the force, you must have made a mistake in arithmetic. When I use your calculated area, I get their force. When I divide the stress by Young's modulus to get the strain, I confirm your value of 0.00137.

So for the force you just multiplied stress with by area ?
If you have time you can work all the problem because I showed it .

we also had a formula F = k delta L , is that another way to find the F ? the only problem is what is the k .
 
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  • #10
chriscarson said:
So for the force you just multiplied stress with by area ? I multiplied area, young modulus and delta L over length
If you have time you can work all the problem because I showed it .
 

What is Young's modulus?

Young's modulus, also known as the modulus of elasticity, is a measure of the stiffness of a material. It describes how much a material will deform under a given amount of stress.

How is Young's modulus calculated?

Young's modulus is calculated by dividing the stress, or applied force per unit area, by the strain, or resulting deformation per unit length. The resulting value is typically measured in units of pressure, such as pounds per square inch (psi) or pascals (Pa).

Why is Young's modulus important for steel bars?

Young's modulus is important for steel bars because it helps determine their structural integrity and ability to withstand external forces. A higher Young's modulus means the steel bar is stiffer and less likely to deform, making it stronger and more suitable for structural applications.

What factors can affect Young's modulus of steel bars?

Several factors can affect Young's modulus of steel bars, including temperature, composition, and manufacturing processes. Higher temperatures can decrease Young's modulus, while impurities in the steel can also affect its stiffness. Additionally, different manufacturing techniques can result in variations in Young's modulus.

How is Young's modulus used in engineering and materials science?

Young's modulus is used in engineering and materials science to design and analyze structures and materials. It provides a measure of a material's ability to withstand stress and deformation, allowing engineers to determine the appropriate materials to use for a specific application. It is also useful in predicting the behavior of materials under different conditions and in identifying potential failure points in a structure.

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