# Is My Tension Calculation Correct in Mechanics Problem?

In summary, the conversation discusses a homework problem regarding a beam and the forces acting on it. The solution involves finding the tension in the cable and the reaction at point C. It is suggested to use a triangle to visualize and solve the problem.

## Homework Equations

$$\sum$$Fx = 0
$$\sum$$MA = 0

## The Attempt at a Solution

for part A, i get 14123N as the tension, moment at C about B, 9.8x1000x5 = 49050
49050/7 = 7007N
tan-1 (4/7) = 29.74o
TSin(29.74) - 7007 = 0
TSin(29.74) = 7007
T=7007/sin(29.74) = 14123N

Is this correct?

Also I had a go at part b, however, went round in circles, so can anyone help me?

Cheers

Andrew

#### Attachments

• Mechanics Tutorial Sheet 1-1.doc
52 KB · Views: 253
There are 3 forces that matter to the beam. First the tension in the cable; second the 1T weight; third the reaction at C. The lines of action of these three must meet at one point if the object is to be in equilibrium from a moment point of view. If you can identify that point of intersection, that will give you the direction of the reaction at C. If you now move those three lines apart to form a triangle, the sides will be in proportion to the forces. You should be able to get it from there. That will incidentally check your first answer for yourself. I accept that there are more algebraic ways of doing this, but with triangles etc, you can see what is going on.

## 1. What is mechanics?

Mechanics is the branch of physics that deals with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of these bodies on their environment.

## 2. What is a free body diagram?

A free body diagram is a visual representation of the forces acting on an object, where the object is isolated from its surroundings and only the external forces acting on it are shown.

## 3. Why are free body diagrams important in mechanics?

Free body diagrams are important in mechanics because they allow us to analyze and understand the forces acting on an object, which is crucial in determining its motion and behavior.

## 4. How do you draw a free body diagram?

To draw a free body diagram, first identify the object and all the external forces acting on it. Then, draw a dot or box to represent the object and draw arrows to represent the magnitude and direction of each force acting on the object.

## 5. Can free body diagrams be used for both stationary and moving objects?

Yes, free body diagrams can be used for both stationary and moving objects. In the case of a stationary object, all the forces acting on the object must be balanced, while in the case of a moving object, the forces must result in a net force that causes the object to accelerate or decelerate.

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