I'm trying to figure out these two problems and I'm so lost! 1. Two planets are circling a star. The second planet has an orbit 4 times the size of the first planet. By the time the first planet revolves once, how many times the second one will? My solution: the formula is T=2PiR/v... so wouldn't the second planet take 4 times as long? 2. Two blocks, which both have the mass of 3kg, are lying on a frictionless surface and are connected by a massless cord. One block is being pulled to the left with a force of 2.5N, and the other block is being pulled to the right with a force of 11.5N. What is the tension of the cord? My solution: Since there's no friction, don't I just subtract the two forces???