1. The problem statement, all variables and given/known data A table of mass 20kg is placed on the ground. A box of mass 3kg is placed on the table. Another box of mass 2kg is placed on the table, not in contact with the first box. Another box of mass 1 kg is placed on top of the 3kg box. The earth, table, and boxes are all at rest. Set up a table for the force that each object exerts on each other object. (1) Fill in the table with the correct values of the forces, treating this as a one-dimensional problem with the +y direction up out of the ground, and the -y direction pointing down toward the center of the earth. Use the rough approximate value g=10m/s2 for the acceleration due to gravity. (There are two more sections, but they are wordy and long, and I think if I get this first part down, they will be much easier, so I'll leave them out for now.) 2. Relevant equations F=ma 3. The attempt at a solution I know there are five objects total, giving me a 5x5 table. An object doesn't exert force on itself (right?), which knocks out some boxes. If g=10m/s2, then I think the table exerts a force of -200N on the table (using F=ma). By Newton's 3rd law, the earth exerts 200N on the table, so my table looks like this so far: View attachment Force exerted.doc When I calculated the force pair of the earth and the table, should I have used the added mass of the table and the objects (meaning the force of the table on the earth would be -260N)? And I'm not sure how to calculate the force by the earth on the objects - does the table's mass interfere? Should I have used the y-component force equation (Fy=F*sin([tex]\theta[/tex])) with an angle of 90 degrees (meaning my other numbers are entirely incorrect), or am I headed in the right direction? I guess I am just wondering if I my calculations are correct so far and where exactly to go next. My professor is very, very vague in his lectures, and writes his own problems, so I find myself a little lost between his lectures and the assignments and my textbooks, because nothing seems to match up, and I'll admit, I don't seem to be that great at physics in general; a push in the right direction would be immensely helpful. Thank you very much (especially for the time you took to read this massive post haha).