Calculating amount of compression a bone can withstand

sruthis

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.

Mapes

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.

sruthis

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.

Mapes

You're already given the stress, you don't need to find it by dividing force by area.

sruthis

ohh. thank you so much. i completely did not realize that F/A was the stress. Thank you thank you.