1. A load of mass 250 kg is lifted vertically using a cable on a pulley system.  The cable is modelled as light and inextensible, and the pulley is modelled as smooth and fixed. The load starts from rest and is lifted with constant acceleration until it is moving with speed 1.2 m s^-1.  During this time, the gravitational potential energy increases by 10 kJ. Use the work-energy principle to find the work done by the tension in the cable during this time and hence find the magnitude of the tension.