A plank of length l = 2m is hinged at one end to a wall. The
other end is being (temporarily) supported by a worker who is
holding it up with his hand, keeping the plank horizontal. The
plank has a mass of 20kg, and there is also a toolbox of mass 5kg
sitting on it, 50cm away from the worker (1.5 m away from the
wall). (a) Draw a free body diagram and an extended free-body
diagram for the...