Calculating amount of compression a bone can withstand

In summary, the conversation involves a person seeking help with a question that involves using the stress = elastic modulus x strain equation. They are given information about a bone's young's modulus and its ability to withstand stress before breaking. The person is then guided to use the equation correctly, with the reminder to carry units along with numbers to avoid errors. They also realize that the stress is already given and does not need to be calculated by dividing force by area.
  • #1
sruthis
7
0
Please I need help with this question. I know I have to use the stress = elastic modulus x strain equation, but i do not know how to apply it to this particular problem.


A Bone has a young's modulus of about 18 x 10^9 Pa. Under compression, it can withstand a stress of about 160 x 10^6 Pa before breaking. Assume that a femur (thighbone) is 0.50 m long, and calculate the amount of compression this bone can withstand before breaking.
 
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  • #2
Hi sruthis, welcome to PF. In this problem, what is the elastic modulus? What is the stress? How is strain related to change in length? You have the right equation, now you just need to apply it correctly. Try to carry the units along with the numbers to avoid making an error.
 
  • #3
I think I need to somehow use the equation F/A = Y(change in L/Linitial) and solve for Linitial, and i guess plug that value into the stress equation? but i do not know how to find A, and I am not sure if I have the right idea.
 
  • #4
You're already given the stress, you don't need to find it by dividing force by area.
 
  • #5
ohh. thank you so much. i completely did not realize that F/A was the stress. Thank you thank you.
 

1. What factors affect the amount of compression a bone can withstand?

The amount of compression a bone can withstand is affected by several factors, including the type and density of the bone, the direction and magnitude of the force applied, and the overall health and condition of the bone.

2. How is the amount of compression a bone can withstand calculated?

The amount of compression a bone can withstand is calculated by dividing the maximum compressive force that the bone can withstand by its cross-sectional area. This value is known as the compressive strength of the bone and is measured in units of stress, typically megapascals (MPa).

3. Can bones withstand more compression than tension?

Yes, bones are generally stronger in compression than in tension. This is because bones are designed to support the weight of the body and resist forces that push or compress them, rather than forces that pull or stretch them.

4. How does age affect the amount of compression a bone can withstand?

As we age, our bones become less dense and more brittle, making them more susceptible to compression forces. This means that older individuals may have a lower amount of compression they can withstand compared to younger individuals.

5. What are some ways to increase the amount of compression a bone can withstand?

Regular weight-bearing exercise, maintaining a healthy diet rich in calcium and vitamin D, and avoiding activities that put excessive strain on the bones can help increase the amount of compression a bone can withstand. Additionally, certain medical treatments like bisphosphonate therapy can also improve bone strength and increase the amount of compression a bone can withstand.

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