1. Fig. 2.1 shows a computer resting on a tabletop that is hunged at A.

   

    

   The tabletop has a mass of 5.0kg and its centre of gravity is 0.40 m from the axis of the hinge at A. The computer has a weight of 200 N acting through a point 0.25m from the hinge at A. The tabletop is supported to maintain it in a horizontal position by a force of F acting vertically at B. The distance AB is 0.80 m.

   a) Calculate the weight if the tabletop.

   weight = ................ N

   (1 Mark)

   b) On Fig. 2.1 draw and label an arrow to reprsent the weight W of the tabletop.

   (1 Mark)

   c) Apply the principle of momentd about the hinge at A to determine the vertical force F applied at B that is required to maintain the tabletop in equilibrium.

   force = F .................... N

   (3 Marks)

   d) The tabletop must experience a resultant force of zero in order to be in equilibrium. Explain how the forces acting on the tabletop fulfill this condition.

   (2 Marks)

   (Marks available: 7)

2. Fig. 4.1 shows the open bonnet of a car. The bonnet is held open at an angle of 60° to the horizontal by a vertical force V applied at one end of the bonnet (shown on the diagram). The bonnst is 0.90 m long, has a weight of 25 N and its centre of gravity G is 0.35 m from the hinge at O.

   

    

   a) On Fig. 4.1, draw and label the two forces other than V acting on the bonnet.

   (2 Marks)

   b) By taking moments about O, show that the vertical force V applied at the end of the bonnet is 9.7 N.

   (2 Marks)

   c) Calclate the magnitude of the force acting at the hinge O. Show your working.

   force at hinge = ............................. N

   (2 Marks)

   (Marks available: 6)

Answer