Question

A 45 kg boy whose leg bones are 5 cm2 in area and 50 cm long falls through a height of 2 m without breaking his leg bones. If the bones can stand a stress of 0.9 × 108 N m2, calculate the Young's modulus for the material of the bone. Use g = 10 ms?​

Answer 1

Here, m = 45 kg, h = 2 m, L = 0.50 m, A = 5 * 10-m2

Loss in gravitational potential

energy = gain in elastic

potential energy in both leg bones

So, mgh = 2xstress x strain x volume

:45x10 x 2 = 2x15x0.9 x 109 x

strain x 2.5 x 10-4

Strain = 0.04

Stress_0.9x10° -2.25x109 Nm2

Y =

Strain

____

0.04

answer is - 2.25×10^9 Nm^-2

Answer 2

see the attachement....