How to Solve for F1 in a Net Torque Problem?

[Arcarius]

Homework Statement

Homework Equations

Net Torque = F1I1 + F2I2

The Attempt at a Solution

In the y direction, the net force is: 0 = F2-Fg, so F2=Fg.
I attempted to do the problem by resolving the net torque, where I defined CW as positive and CCW as negative, so I got: Net Torque = (0.750m)F1 - (0.250m)Fg + dFg. I don't know how to find the distance d in the Net Torque equation, which is keeping me from getting F1.

 

[collinsmark]

In the y direction, the net force is: 0 = F2-Fg, so F2=Fg.
I attempted to do the problem by resolving the net torque, where I defined CW as positive and CCW as negative, so I got: Net Torque = (0.750m)F1 - (0.250m)Fg + dFg. I don't know how to find the distance d in the Net Torque equation, which is keeping me from getting F1.

Forgive me, but I'm unable to follow your notation. What is Fg referring to? What's d mean? They are not indicated in the problem statement, nor the diagram.

Maybe you could use F₁ for the force of the table on the first support (at 1), F₂ for the force of the table on the second support (at 2), and Mg (as in M times g) for the force of gravity on the chair and child.

Here is a hint on how to do this problem: Nothing is accelerating, even rotationally. So you know all torques (moments) around a given point is zero. First you'll need to pick a point around which to take a moment. Any point will do, but some points are more logical than others (and a couple of points you'll want to avoid). You'll make this problem a lot easier on yourself if you take the moment around point 2, since you don't already know what the force is at that point (i.e. there isn't a known force there that would help solve the problem anyway), the problem statement isn't asking for the force at that point, and distances are given to you relative to that point.