4.40 .. cp two blocks connected by a light horizontal rope sit at rest on a horizontal, frictionless surface. block a has mass 15.0 kg, and block b has mass m. a constant horizontal force f = 60.0 n is applied to block a (fig. p4.40). in the first 5.00 s after the force is applied, block a moves 18.0 m to the right. (a) while the blocks are moving, what is the tension t in the rope that connects the two blocks? (b) what is the mass of block b?