Problem: If you hold your arm outstretched with palm upward, as in the figure, the force to keep your arm from falling comes from your deltoid muscle. The arm of a typical person has a mass of 4.0kg and the distances and angles are shown in the figure. a. What force must the deltoid muscle provide to keep the arm in this position? b. By what factor does the force exceed the weight of the arm?
FREE Expert Solution
Torque;
(a)
The weight of the arm creates a clockwise torque, while the Deltoid muscle creates a counter-clockwise torque.
Tcw = r•mg sinθ = 0.38 × 4.0 × 9.8 × sin 90
Tccw = r•FD sinθ = 0.17 × FD × sin 15
Problem Details
If you hold your arm outstretched with palm upward, as in the figure, the force to keep your arm from falling comes from your deltoid muscle. The arm of a typical person has a mass of 4.0kg and the distances and angles are shown in the figure.
a. What force must the deltoid muscle provide to keep the arm in this position?
b. By what factor does the force exceed the weight of the arm?
Frequently Asked Questions
What scientific concept do you need to know in order to solve this problem?
Our tutors have indicated that to solve this problem you will need to apply the Torque Due to Weight concept. You can view video lessons to learn Torque Due to Weight. Or if you need more Torque Due to Weight practice, you can also practice Torque Due to Weight practice problems.
What professor is this problem relevant for?
Based on our data, we think this problem is relevant for Professor Johnson's class at Johnson County Community College.