equilibrium

[Scott55]

This is an equilibrium problem. I do not know where to start, I usually do not run into this problem but for some reason I cannot start this problem.

Here is the question: Given a table with four light legs equally spaced around the circumference of a uniform circular top weighting 80N, find the smallest weight that, when placed on the table, will be able to upset it.

Thank you.

[Doc Al]

Originally posted by Scott55
This is an equilibrium problem. I do not know where to start, I usually do not run into this problem but for some reason I cannot start this problem.

First draw yourself a picture of the table and the four legs. Where is the best place to push down if you wanted to tip it over? (Hint: it's not the center!)

To find how much weight you need, first find the fulcrum about which the table will tilt. Then consider rotational equilibrium about that point. When the torque of the added weight just balances the torque due to the weight of the table, the table will start to tip.