14. Exercises

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Exercise14.1

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

Image:E14.1.GIF

(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.



Exercise 14.2

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.

Image:E14.2.GIF



Exercise 14.3

A uniform beam has mass 20 kg and length 6 m. It rests on two supports that are 1.5 m from each end of the beam. A concrete block of mass 5 kg is placed at a point on the beam at a distance of 2.5 m from one end. Find the magnitude of the reaction forces exerted on the beam by the two supports.



Exercise 14.4

A uniform rod of mass 18 kg and length 6m rests on two supports.


Image:E14.4.GIF


a) Find the magnitude of each force exerted on the rod by the supports.

A particle is attached to the rod at the right hand end.

b) What is the greatest possible mass of the particle if the rod remains in equilibrium?



Exercise 14.5