The sketch shows a mobile in equilibrium. Each of the rods is 0.16 m long, and each hangs from a supporting string that is attached one fourth of the way across it. The mass of each rod is 0.10 kg. The mass of the strings connecting the blocks to the rods is negligible. What is the mass of (a) block A? (b) block B?
I can't get the sketch on here.. but I will try and explain it. The origin string is attached to a rod and a string is attached holding block B on the right end and a string holding another rod on the left end. That rod is holding a string with a 0.30kg block on the left and a string with block A on the right. I assume that A is heavier than 0.30 because the string is tied to the rod closer to block A than the 0.30kg block.