# Forearm Homework: Finding Forces, Tension, Moment WRT Elbow Point E

• Ronaldo95163
In summary, the conversation discusses a system of forces acting on the human forearm, with a weight of 25N acting at a distance of 15cm from the elbow. The goal is to find the force exerted by the muscle in the upper arm, the forces acting at the elbow, and the tension when theta is 45 degrees. The equation for sum of ACW and CW is mentioned, and the mechanical disadvantage of this type of lever is also discussed. The solution involves solving for E using moments and then substituting it into the equation to find for F.
Ronaldo95163

## Homework Statement

Figure 5 below shows an approximation of the system of forces acting on the human forearm. The weight of the forearm is 25N and acts 15cm from the elbow of a girl lifting a dumbbell of weight 50N

Find the
1)Force, F, exerted on the human forearm by the muscle in the upper arm
2)Forces acting at the point, E of the elbow
3)Tension if theta is 45 degrees

## Homework Equations

sum of ACW = sum of CW
sum of upward forces = sum of downward forces

## The Attempt at a Solution

My Attempt is in the pictures below

#### Attachments

• img1.jpg
12.6 KB · Views: 376
• img2.jpg
15.3 KB · Views: 346
• img3.jpg
16.2 KB · Views: 373
Hi Ronaldo95163. You could use ∑ forces iff you knew the force acting at the elbow, but we don't know anything about force components at E (apart from the fact that they exist). So your first part is wrong. You will have to approach it differently.

In any case, because of the big mechanical disadvantage seen in this type of lever, you know that the upwards force needed close to the pivot point is going to be >> the two downward forces you have considered.

Thanks a lot man...wasn't sure if to consider thet force at E first...what I figured tho was that
Fsin70 = 75 + E

Solve for E using moments and then substitute it into find for F

## 1. What is the purpose of "Forearm Homework: Finding Forces, Tension, Moment WRT Elbow Point E"?

The purpose of this homework is to use the principles of mechanics to analyze and solve problems related to forces, tension, and moments in the forearm. This can help us understand the biomechanics of the human body and how different forces can affect it.

## 2. What are the key concepts involved in this homework?

The key concepts involved in this homework include Newton's Laws of Motion, equilibrium, tension, and moment of a force. It also requires an understanding of basic trigonometry and vector analysis.

## 3. How can this homework be used in real life?

This homework can be applied to real-life situations such as sports, physical therapy, and ergonomics. For example, understanding the forces and moments in the forearm can help athletes improve their performance and prevent injuries. It can also be used to design ergonomic tools and equipment that reduce strain on the body.

## 4. What are some common mistakes students make when solving "Forearm Homework: Finding Forces, Tension, Moment WRT Elbow Point E"?

Some common mistakes students make include not properly identifying all the forces acting on the forearm, not using the correct equations or not setting up the equations correctly, and not considering the direction and magnitude of the forces. It is also important to pay attention to units and conversions when solving the problems.

## 5. How can I improve my problem-solving skills for this homework?

To improve your problem-solving skills for this homework, it is important to have a good understanding of the underlying concepts and to practice solving similar problems. It can also be helpful to break down the problem into smaller parts and draw diagrams to visualize the forces and moments. Additionally, seeking help from a teacher or tutor can provide valuable guidance and feedback.

Replies
20
Views
2K
Replies
6
Views
1K
Replies
10
Views
8K
Replies
2
Views
3K
Replies
4
Views
3K
Replies
1
Views
2K
Replies
7
Views
6K
Replies
4
Views
9K
Replies
1
Views
2K
Replies
8
Views
5K