Static Equilibrium of deltoid muscle

Click For Summary

Homework Help Overview

The discussion revolves around calculating the forces involved in the static equilibrium of the deltoid muscle while holding an outstretched arm. The problem specifically addresses the force required by the deltoid muscle and the force exerted by the shoulder joint, given the mass of the arm.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply equations of static equilibrium based on a previous similar problem, raising questions about the impact of removing an external weight from the scenario.
  • Some participants question whether to exclude the weight force entirely or modify the existing equations to account for the absence of that weight.
  • Another participant provides an alternative calculation for the force required by the deltoid muscle, suggesting a different approach to the problem.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem setup and the implications of removing the weight. Some guidance has been offered regarding the exclusion of certain forces, but no consensus has been reached on how to adjust the equations accordingly.

Contextual Notes

Participants are navigating the constraints of the problem, particularly the changes in calculations when external weights are present or absent. The original poster references a previous class problem that involved a different weight, which may influence their approach to this problem.

Bones
Messages
108
Reaction score
0

Homework Statement


Calculate the magnitude of the force, FM, required of the "deltoid" muscle to hold up the outstretched arm shown in the figure. The total mass of the arm is 3.3 kg. Then, calculate the magnitude of the force FJ exerted by the shoulder joint on the upper arm.
http://www.webassign.net/gianpse4/12-56.gif



Homework Equations





The Attempt at a Solution


We did a problem similar to this in class, but there was a 8.5kg object in the hand.
X direction:
Fjcos(theta)-Fmcos15=0

Y direction: Force of weight=32.2N
-Fjsin(theta)+Fmsin15 Force of object=83.3N
-32.3N-83.3N=0

tnet=Fm(0.12m)(sin15)-32.3N(0.24m)(sin90)-83.3N(0.52m)(sin90)=0
Fm=1644N

How would you this problem change is there is no weight in the hand like the above problem suggests?
 
Physics news on Phys.org
If there was no weight, you would not include the force of gravity from that weight or the torque caused by that force in your calculations.
 
Does this mean I just leave it out or do I alter the equation in some way?
 
I got part a:
tnet=mg(24m)-Fmsin15(0.12m)=0
Fmsin15(0.12m)=(3.3kg)(9.8m/s^2)(0.24m)
Fm=(3.3kg)(9.8m/s^2)(0.24m)/0.03106m
Fm=250N

How do I figure out Fj for part b?
 

Similar threads

Arm problem, Static Equilibrium
  • · Replies 1 ·
Replies
1
Views
16K
Calculating the Force of the Deltoid Muscle to Raise an Arm
  • · Replies 4 ·
Replies
4
Views
3K
How Does the Deltoid Muscle Maintain Arm's Static Equilibrium?
  • · Replies 1 ·
Replies
1
Views
30K
Static equilibrium and torque problem
  • · Replies 5 ·
Replies
5
Views
14K
Moment of force and static equilibrium
  • · Replies 2 ·
Replies
2
Views
4K
Equilibrium when applied to muscles and joints Help, please
  • · Replies 2 ·
Replies
2
Views
16K
Rotational dynamics and static equilibrium question
  • · Replies 1 ·
Replies
1
Views
5K
What Is the Required Muscle Force to Hold an Outstretched Arm?
  • · Replies 2 ·
Replies
2
Views
10K
Graduate Equilibrium in the Human Body using Torque
  • · Replies 1 ·
Replies
1
Views
7K
Lifting Baby Safely: Calculating Tension in Backbone
  • · Replies 2 ·
Replies
2
Views
2K