cameroon gce A level 2024 mechanical design 2
cameroon gce A level 2024 mechanical design 2
SECTION A:STATICS
(Answer ALL Questions)
QUESTION 1:
The bulldozer proposed in figure 1 below is used at a worksite to tamp and level the ground. The machine is constituted
of a bulldozer blade 2 articulate at C on the chassis!of the bulldozer. The adjustment of the blade position is ensured b
the hydraulic jack 3+4 (3 = body, 4 = rod). The hydraulic jack is articulated at B on the chassis and at A on the build *
blade 2. The links at A, B and C arc pivot links that bear the same names.
/10 Marks
ozer
Hypotheses:
This study is done in the plane of symmetry of the machine which is the one of the figure 1;
The mechanical action of the hydraulic jack 3+4 on the bulldozer blade 2 at A is directed upward;
– The whole system is considered to be in equilibrium;
F(10 000 daN) represents the action applied by the ground 0 on the bulldozer blade and P (4 000 daN) the
self–weight of the bulldozer blade.
The aim of the study is to determine the hydraulic jack diameter and mechanical action acting at the level of the
articulations: A, B and C.
1. Study of the equilibrium of hydraulic jack (3+4)
1.1 Isolate the hydraulic jack (3+4).
1.2 Apply the FPS and conclude about the line of action of the mechanical actions
| acting at A and B. 2. Study of the equilibrium of the bulldozer blade 2. |
(2 marks) |
2.1 Isolate the bulldozer blade 2.
(1 mark)
(1 mark)
2.2 Make the inventory of all the mechanical actions acting on it and determine all the unknown mechanical
actions. (4 marks)
3. Determine the diameter of the piston rod of the hydraulic jack knowing that the pressure developed on the
QUESTION 2: /10 Marks
The drawing in figure 2 below represents a manual perforator. The device comprises of the lever 1 articulated at A on the
body 3 and is supported by the cylindrical punch 2 at B. The mechanical action of the operator provokes displacement of
the cylindrical punch 2 and correspondingly perforates the writing paper pad 4.
Hypotheses:
The contact between the cylindrical punch and the body is assumed taking place at C and D;
At points C and D there is friction contact with the coefficient of friction f=0.26.
The magnitude of the mechanical action of the operator on the cylindrical punch is ||fx) jj =50 N.
The study is done in the plane of symmetry which is the one of the drawing represented in figure 2 below.
1. Graphical study of the cylindrical punch 2.
1.1 Isolate the cylindrical punch 2.
1.2 Make the inventory of all the external forces acting on
external mechanical actions.
1.3 Choose among the methods below the suitable method used to determine all the unknown forces acting on the
| cylindrical punch 2 |
