A block with a mass of 1 kilogram is attached by a lightweight, but strong rope to a second block with a mass of 2 kilogram. The rope runs over a pulley (which is ideal, the pulley has a mass less sheave and a frictionless axle), thus that both masses hang from the pulley. The heavier block accelerates downwards, and the lighter block accelerates upwards. Obtain the tension in the rope between the masses?