Free+Body+Diagram

=__**Free Body Diagram**__= toc The free body diagram is one of the most important concept in physics. Vectors from Ch.3 are used in free body diagrams. It applies itself in forces, energy, momentum, collisions, torque, electricity, and magnetism. But first lets look at how to make a free body diagram.

__**Steps On Making A Free Body Diagram**__
1) Read the problem carefully

2) Draw a picture of the problem

3) Label all forces that act on the object and abbreviate words with letters.
 * Ex: T for Tension

4) Once all forces are labeled draw a //x// and //y// graph and copy all the forces drawn from the picture to the //x// and //y// graph.

5) If a force is at an angle then break up the forces in //x// and //y components//.
 * Ex:

6) Once all the forces and its components are labeled make a custom equation that fits the system.
 * Be careful! There are usually two or more unknowns in the equation and one must be solved in order to solve the others

7)Objects that are at rest or moving with constant velocity are said to be in equilibrium.

__**Example Problem**__
lets do an example problem and apply all of the steps.

So the problem is asking for three tensions and there is already a picture drawn so that completes steps one and two. The bird feeder is supported by three cables and is at rest which means its an equilibrium problem. We have applied step 7 and now we apply step 3.



So we have the weight,W, of the bird feeder is going down, T1 pulling the bird feeder up, and T2 and T3 are supporting T1. Now we apply step 4 and step 5.



Now that all the forces and its components are labeled we apply step 6, making the custom equation for both free bodies.

For the first diagram the formula is



For the second diagram the equations are



First lets solve the first diagram equation. So we add weight,W, on both side of the equation and we get T1 equals to W. Since W is 150N then T1 equals 150N.



Now lets solve the second diagram equation. First lets solve for Fx. We add (T2)(cos60) on both sides of the equation. Then divide cos60 on both sides and get



Then we simplify and get



We use Fy equation and substitute T2 with T3(1.732) and solve for T1.



Factor out the T3



Simplify and we get



Lets use one of the previous equations, which is



Lets substitute what we got for T3 which is 75N and then simply and get



We have now solved a problem using a free body diagram and applying all of the steps of a free body diagram. I hope this example problem helps you understand more of a free body diagram and how to approach it =)

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