14. Exercises

A uniform beam of mass 20 kg and length 3m rests on two supports as shown below.

(a) Find the reaction force exerted by each support.

(b) Find the greatest mass that can be placed at the left hand end of the beam.

A plank has length 6 m. The plank is placed on a quayside with its mid-point at the edge of the quay, so that half of the plank sticks out over the water. A rock of mass m kg, which should be modeled as a particle is placed at the end of the plank which is on the ground. A person of mass 60 kg walks on the part of plank that is over the water. When the person is 1 m from the end the plank is on the point of tipping. Find m.