Calculation Help Needed

1. Apr 7, 2007

Air

1. The problem statement, all variables and given/known data
Find the mass:

2. Relevant equations
Not Sure.

3. The attempt at a solution
I don't know where to start as I believe that there is less information.

All that I have got upto is Tan-1(3/8) but I don't know if this is needed to find the mass?

2. Apr 7, 2007

Hootenanny

Staff Emeritus
I'm assuming the frame is massless, pivoted bout the right angle of the triangle and the system is in equilibrium, am I correct?

3. Apr 7, 2007

Air

Yes, You are correct.

4. Apr 7, 2007

Hootenanny

Staff Emeritus
So, we know that since the system is in equilibrium, the sum of the moments about any point should be zero. However, lets consider the forces; if the system is not translating (i.e. moving up or down) what must be the vector sum of the vertical forces?

5. Apr 7, 2007

Air

Erm...Not sure but guessing zero.

6. Apr 7, 2007

Hootenanny

Staff Emeritus
Sounds good to me and where will this reation force be applied?

7. Apr 7, 2007

Air

Either at the angle at the end of Y or near the mass?

8. Apr 7, 2007

Hootenanny

Staff Emeritus
Normal forces are applied at the point where the system pivots. Just checking, is the side x attached to a wall of some kind?

9. Apr 7, 2007

Air

Nope. The pivot is at the corner of x and y.

x and y dimensions are given if to calculate the angle (I think).

10. Apr 7, 2007

Hootenanny

Staff Emeritus
Okay, let us consider the torques about the pivot point;

$$0.08T\sin\left(\arctan\left(\frac{3}{8}\right)\right) = 0.4mg$$

Where T is the tension in the diagonal member. Do you follow?

Last edited: Apr 7, 2007
11. Apr 7, 2007

Air

Yes, I do.

12. Apr 7, 2007

Air

Can Tension be calculated without mass?

13. Apr 7, 2007

arildno

You still have not set up the equalibrium of FORCES, only of torques..

$$\sin(\arctan(x))=\frac{x}{\sqrt{1+x^{2}}}$$