Stress and strain, maximum applied force before permanent deformation/breakage


by wolfpack11
Tags: applied, force, maximum, permanent, strain, stress
wolfpack11
wolfpack11 is offline
#1
Jun19-12, 06:00 PM
P: 4
Compute the maximum longitudinal force that may be supported by a bone before breaking, given that the compressive stress at which bone breaks is 2.00e8 N/m^2. Treat the bone as a solid cylinder of radius 1.55 cm


. The attempt at a solution
I tried using the equation Max Torque = pi/4 * (r^3) * max stress. Plugged in 0.0155 m for "r" and 2.00e8 N/m^2 for max stress, got 585 N*m for torque, then divided again by 0.0155 m to get the Force (377000 N). This answer wasn't accepted into webassign. What am i missing in the problem solving?
Phys.Org News Partner Science news on Phys.org
Cougars' diverse diet helped them survive the Pleistocene mass extinction
Cyber risks can cause disruption on scale of 2008 crisis, study says
Mantis shrimp stronger than airplanes
PhanthomJay
PhanthomJay is offline
#2
Jun19-12, 10:46 PM
Sci Advisor
HW Helper
PF Gold
PhanthomJay's Avatar
P: 5,966
You are calculating max torque or moment due to bending stresses, but the problem is asking, perhaps not too clearly, for max axial (longitudinal) load based on allowable axial stress. Instead of using bending stress = M/S, try using axial stress = P/A.
wolfpack11
wolfpack11 is offline
#3
Jun20-12, 11:09 AM
P: 4
Ok. If P is the compressive force, and A is the cross-sectional area that the force is applied to, I would think that A= ∏*r^2 for the surface of the cylinder. Then, multiplying A by the maximum stress 2e8 N*m^2 would yield P?

PhanthomJay
PhanthomJay is offline
#4
Jun20-12, 03:06 PM
Sci Advisor
HW Helper
PF Gold
PhanthomJay's Avatar
P: 5,966

Stress and strain, maximum applied force before permanent deformation/breakage


Yes.


Register to reply

Related Discussions
Maximum Force Applied to Brakes Introductory Physics Homework 1
Stress vs. Strain and finding the permanent set of bar Engineering, Comp Sci, & Technology Homework 0
Determining maximum force applied on a lever Engineering, Comp Sci, & Technology Homework 11
Stress-strain diagram using deformation ? Engineering, Comp Sci, & Technology Homework 2
Permanent magnets & maximum force Classical Physics 3