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I took this problem from

*Vector Mechanics for Engineers*by Beer et al. The reason why I am writing this is because I don't understand where I am wrong in this problem, yet I know I am wrong.

This is problem 6.123 and it's a problem concerning analysis of structures (in this case a machine).

https://scontent-lax3-1.xx.fbcdn.net/v/t1.0-9/13590368_1744245399193330_1531717957213866948_n.jpg?oh=b73b768c39128c189fcca2f3a5d3e3f4&oe=5835700D

So the first thing I did was calculating the reactions the system has. In this case there is a reaction in node

**A**which consists of a

**rough surface**. Therefore there are two forces which is in fact one single force but decomposed into its horizontal and vertical components which I called A

_{x}and A

_{y}respectively.

https://scontent-lax3-1.xx.fbcdn.net/v/t1.0-9/13567002_1744248252526378_7606622242639327423_n.jpg?oh=23ec4d5bd163fcbba959ba52711e8d41&oe=57F96698

This is where my problem begins, lets suppose I just considered the reactions

**A**and

_{x}**A**in node

_{y}**A**and the

**250 N**load acting in node

**C**. Then I work with equilibrium equations:

[itex]\sum F_{x}=0[/itex]

[itex]\sum F_{y}=0[/itex]

For the equation [itex]\sum F_{x}=0[/itex] we find out that the only force acting upon the x-axis is the horizontal component

**A**that becomes zero. Then for the other equation [itex]\sum F_{y}=0[/itex] I see that there are two forces: the

_{x}**250 N**that goes

**downwards**and the

**A**that I supposed that goes

_{y}**upwards**. When I perform the operations required I get that the A

_{y}force is

**250 N**that goes upwards. Since the vertical component is the only component for the reaction in node A then I conclude that the reaction in node A is

**250 N upwards**.

So far we have answered part b).

When I consult the answers to selected problems section just to verify I am right I see that the answer doesn't match:

https://scontent-lax3-1.xx.fbcdn.net/v/t1.0-9/13511060_1744249799192890_8621689707186190488_n.jpg?oh=cd46cd6c0101d44c8d8a4d65b6dd0a2b&oe=57FB23BC

It is not that the answer doesn't match in magnitude, but it also says that the reaction has an angle of 61.3°.

I don't know where I am wrong.

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