# Homework Help: Force of lifting tongs

1. Apr 17, 2013

### Gauss M.D.

1. The problem statement, all variables and given/known data

See attachment

2. Relevant equations

3. The attempt at a solution

I think I just need a kickstart figuring out what the forces in the vertical direction of F and G are. I am guessing F and G are exerting a force in the direction of their normal, but I have no idea how to figure out the angle of that normal. Really lost :(

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2. Apr 17, 2013

### haruspex

You can solve this by concentrating on the tongs as the 'free bodies'. The load applies a vertically downward force Mg/2 on each, and you just need to compute the horizontal force it must apply in equilibrium.
Another approach is to think in terms of mechanical advantage. If the load were to descend some small distance dy, how much closer would the ends of the tongs get?

3. Apr 18, 2013

### Gauss M.D.

Thanks for the help. I can't seem to work out the coordinates of points A or B however. I think I need those to calculate moments, but I'm not sure how to find them...

4. Apr 18, 2013

### haruspex

It is not possible to determine the co-ordinates of those points, but it turns out not to matter.
Can you find the tension in the rod DE? Can you then take moments about F in rod DAF?