3. A packing-case, of mass 60 kg , is standing on the floor of a lift. The mass of the lift-cage is 200 kg . The lift-cage is raised and lowered by means of a cable attached to its roof. In each of the following cases, find the magnitude of the force exerted by the floor of the liftcage on the packing-case and the tension in the cable supporting the lift:

1. The lift is descending with constant speed.
2. The lift is ascending and accelerating at \(1.2 \mathrm {~ms} ^ { - 2 }\).
3. State any modelling assumptions you have made.