- #1
Puchinita5
- 183
- 0
Homework Statement
In Fig. 12-35, a uniform beam of weight 500 N and length 3.0 m is suspended horizontally. On the left it is hinged to a wall; on the right it is supported by a cable bolted to the wall at distance D above the beam. The least tension that will snap the cable is 1200 N. (a) What value of D corresponds to that tension? (b) To prevent the cable from snapping, should D be increased or decreased from that value?
Homework Equations
http://edugen.wiley.com/edugen/courses/crs1650/art/images/halliday8019c12/image_t/tfg035.gif
The Attempt at a Solution
ok i don't actually need anyone to solve this question. I am having trouble with a minor concept.
To begin, I wanted to set the Torques equal to zero. When calculating the Torque for the tension however, i am confused about the angle between r and F. From all my studies, I feel like the angle between r x F should be the obtuse angle outside the triangle. As in, if I were to keep extending the lever out towards the right, the angle between this and the tension angle. However, When I set my torque equation, i get a very small number for the angle, which suggests that it has given me the interior angle. But conceptually i don't see how this could be. I don't know if that makes sense. But if anyone has any clarification for me I would really appreciate it.
I had:
(1200)(3)sin(theta)-(500)(1.5)=0
which gives me theta=12.02...