Physics in biology and medicine (spring/compression) PLEASE HELP, THANK YOU

[futuredoc206]

Physics in biology and medicine (spring/compression)... PLEASE HELP, THANK YOU

Homework Statement

A person falls from some height before catching themselves by their fingers (one hand) on a lodge. If each of the four fingers is treated as a 3 cm long bone with a cross-sectional area of 3.0cm^2 per finger, a fall from what height would result in broken fingers? Assume that they have a total body mass of 70 kg.

Homework Equations

h=(area)(length)(stress^2 of broken finger)/ (2)(young's modulus)(mass)(gravity)
Cross-sectional area = 3.0cm^2 per finger
total body mass = 70kg
stress of broken fingers/rupture strength = 100 x 10^7 dyn/cm^2
length of each of the 4 fingers = 3cm
young's modulus of bone = 14 x 10^10 dyn/cm^2
gravity = 9.8 m/s^2

The Attempt at a Solution

change mass (kg) to mass (g) = 70kg x (1000g)/(1kg) = 70000g/4 fingers = 17500g
change stress (x 10^7) to stress (x 10^9) = move decimal 2 places = 1 x 10^9 dyn/cm^2
change gravity (m) to gravity (cm) = 9.8m/s^2 x (1000cm/s^2)/(1m/s^2) = 980cm/s^2
now I plug in the problem:
h= (3.0cm^2)(3cm)(1x10^9dyn/cm^2)^2/(2)(14x10^10dyn/cm^2)(17500g)(980cm/s^2)
h=2cm or 0.064ft

Please help me by letting me know if I am headed in the right direction or not... Thanks in advance for your help

 

[vela]

Looks fine to me. (That is, as long as the assumption that all the energy gets stored in the finger bones is acceptable for solving this problem.)

 

[futuredoc206]

Vela... Thank you so much for the reply