Compression of human bone: forces

[maxd23]

Homework Statement

While unrealistic, we will examine the forces on a leg when one falls from a height by approximating the leg as a uniform cylinder of bone with a diameter of 2.3 cm and ignoring any shear forces. Human bone can be compressed with approximately 1.7 × 10^8 N/m2 before breaking. A man with a mass of 80 kg falls from a height of 5 m. Assume his acceleration once he hits the ground is constant. For these calculations, g = 10 m/s2.

With how much force can the "leg" be compressed before breaking?

Homework Equations

The Attempt at a Solution

The correct answer:
I’m confused about how the answer is 7.1E4 N , can you explain how to get this answer from the data given?

wouldn’t it be F = (1.7 × 10^8 N/m2)*(2.3cm(1m/100cm)^2 = 3.9E4 N ?

 

[TSny]

Looks like you are using the square of the diameter of the cylinder for the area. What is the formula for the area of a circle?

 

[maxd23]

A=pi(r^2)
Ahhh I see! lifesaver over here.