posted by m2a .
A massless string runs around two massless, frictionless pulleys. An object with mass m = 20 kg hangs from one pulley. A force F is exerted on the free end of the string to lift the object at a constant speed by a distance of 2.3 m. What is the work done on the object by the force F? Hint: Use the lower pulley and the attached object as the system and note that the force F is the tension in the string.
work done on gravity= 20*g*2.3m
This has to be the work done by F also.