FindingTension, Dissimilar Angles.

[Coquelicotte]

I'd just like to say that even lurking this forum is a great help to users. (:

Homework Statement

http://img260.imageshack.us/img260/5679/scan001001cz9.jpg

Homework Equations

I'm assuming, since this is all I've had to work with for weeks, trig. relationships such as: SIN, COS, TAN and their inverses.

The Attempt at a Solution

http://img216.imageshack.us/img216/1033/scan001001sie6.jpg

Now, the obvious problem with what I've done, I think, is that I've treated it as if the angles were the same, correct? I think so. The thing is, I'm not sure how to do it any other way.

I'm also unsure as to how to handle finding Cord C's tension the correct way. Wouldn't it simply be the given weight, since it is a vertical line?

Thanks for your time.

 

[learningphysics]

Cord C is correct. 200N. You can get this by taking the freebody diagram of the suspended mass. There are only two forces. The tension in the cord, and the weight.

Always decide what you're taking the freebody diagram of first... this is the most important step.

You need to get T1 and T2. What can you take the freebody diagram of? Draw a circle around the body you're taking the freebody diagram of...

 

[Coquelicotte]

The body I am taking the free body diagram of? Isn't that my first picture?

 

[learningphysics]

The body I am taking the free body diagram of? Isn't that my first picture?

No. In your picture... draw a circle around what exactly you wish to examine... For example I could draw a circle around the suspended mass. So my freebody is whatever is inside the circle... what are the external forces acting on whatever is inside the circle? There's the tension in cord C, and the weight of the mass...

So immediately I get: Tc - mg = 0, and I can solve for Tc

Now to get the other 2 tensions, I need a different freebody... I draw a circle around the mass and the entire cord C... ie the two other cords intersect my circle... What are the external forces acting on whatever is inside the circle? I can do F=ma in the x and y directions, and then solve for the tensions.