Bone has a Young's modulus of about
1.8 x 100 Pa. Under compression, it can
withstand a stress of about 1.58 x 10° Pa be-
fore breaking.
Assume that a femur (thigh bone) is 0.54 m
long, and calculate the amount of compression
this bone can withstand before breaking.
Answer in units of mm.

Respuesta :

Answer: 4.74 mm

Explanation:

We can solve this problem with the following equation:

[tex]Y=\frac{stress}{strain}[/tex] (1)

Where:

[tex]Y=1.8(10)^{10} Pa[/tex] is the Young modulus for femur

[tex]stress=\frac{F}{A}=1.58(10)^{8} Pa[/tex] is the stress (force [tex]F[/tex] applied per unit of transversal area [tex]A[/tex]) on the femur

[tex]strain=\frac{\Delta l}{l_{o}}[/tex]

Being:

[tex]\Delta l[/tex] the compression the femur can withstand before breaking

[tex]l_{o}=0.54 m[/tex] is the length of the femur without compression

Writing the data in equation (1):

[tex]Y=\frac{\frac{F}{A}}{\frac{\Delta l}{l_{o}}}[/tex] (2)

[tex]1.8(10)^{10} Pa=\frac{1.58(10)^{8} Pa}{\frac{\Delta l}{0.54 m}}[/tex] (3)

Isolating [tex]\Delta l[/tex]:

[tex]\Delta l=\frac{(1.58(10)^{8} Pa)(0.54 m)}{1.8(10)^{10} Pa}[/tex] (4)

[tex]\Delta l=0.00474 m[/tex] (5) This is the compression in meters

Converting this result to millimeters:

[tex]\Delta l=0.00474 m \frac{1000 mm}{1 m}=4.74 mm[/tex]

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