Homework Help: Little help with practice problem for exam. (tension in strings)

1. Sep 22, 2004

tibu

Hello, I'm new here. Basically I have this practice excercise for my exam.:

http://capa.hep.uprm.edu/msuphysicslib/Graphics/Gtype06/prob09_xph183f6pic2.gif [Broken]

My general problem is that I'm bad with separating forces into components, and I assume this excercise deals with that. Can someone plz point me in the right direction to solving this problem? Any help will be greatly appreciated.

Last edited by a moderator: May 1, 2017
2. Sep 22, 2004

Sirus

Always begin these types of problems with a free-body diagram (draw each force vector acting on the object). Remember that since the object is in equilibrium, all the force vectors, when added vectorally, should give zero. Use that and the angle and mass given, and you should be able to solve this.

3. Sep 22, 2004

tibu

Ok i believe that in order to get the tension in the horizontal string, I I need to get the horizontal component of the upper string since the lower string doesnt have a vertical component.

But the angle they give me is kinda weird.

I tried setting the tension in the lower string ewual to m*g*cos(27) but that does not give me the correct answer...

4. Sep 22, 2004

Sirus

In this case, doing trigonometric vector analysis is easier. Use vector addition to create a force-vector triangle, then use trigonometry (should be easy once you have the right triangle).

5. Sep 22, 2004

tibu

... :uhh: You lost me on the last one.

6. Sep 22, 2004

Sirus

Sorry. Have you learned how to do vector addition and analysis? Draw all the vectors for the forces present, then place them tip to tail, and fill in angle and magnitude values, which gives you a right-angle triangle (in this case) with two side lengths and an angle, meaning you can find all the other info.

7. Sep 22, 2004

tibu

Ok I did this but what are the side lengths? The angle is the 90deg one right?