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Cork Institute of Technology
Bachelor of Engineering in Mechanical Engineering – Stage 1
(NFQ Level 7)
Summer 2007
Engineering Science 1
(Time: 3 Hours)
INSTRUCTIONS Answer FIVE questions All questions carry a total of 20 marks.
Examiners: Ms. M. Kavanagh Mr. J. Connolly Dr. P. Delassus
Q1 (a) An eye bolt is subjected to two forces of 250N and 150N in the directions shown in Fig 1. Determine the resultant force. (8 marks)
Fig 1
(b) Using (a) above as an example, distinguish between the resultant force and the equilibrant. (2 marks) (c) Determine the tensions in the ropes attached to the rigid supports in the system shown in Fig 2 if the supported block is in equilibrium. The block has a mass of 12kg. (10 marks)
Fig 2
Q2. A tram which travels backwards and forwards between terminal A and terminal B can accelerate at 2.5m/s^2 and decelerate at 3.1m/s^2. Its maximum velocity is 35m/s. Draw the velocity-time graph for the tram and calculate the shortest time to travel from terminal A to terminal B, a distance of 1580m, if the tram makes no stops on the way. Calculate the time if the tram makes one stop of 10seconds duration. (20 marks)
Q3 (a) A train of total mass 90 t is travelling at 90 km/h on a level track. The track resistance is 90 N/t. Calculate the breaking effort required to stop the train in one minute. (5 marks) (b) A car of mass 1 tonne draws a caravan of mass 0.75 tonne. If the car engine produces a tractive effort of 4kN and there is a resistance to motion of 80N per tonne on the car and 70N per tonne on the caravan calculate; (i) the acceleration and (ii) the tension in the car tow bar. (15 marks)
Q4 (a) Calculate by moments the magnitude of both reaction forces Rbc and Rcd at the supports of the framework shown in Fig 3. (5 marks)
(b) Graphically determine the forces in each of the members AF, FE, EC and ED. Indicate for each member if it is in compression or in tension. (15 marks)
Fig 3
θ
Q7 A body of mass 5 kg is placed on an inclined slope of 30 0. The coefficient of friction, (^) μ, between the contact surfaces is 0.4.
(a) If no force is applied to the body, show by means of calculation what will happen. (8 marks) (b) Calculate the force (parallel to the inclined plane) that must be applied to stop the body sliding down the plane. (4 marks) (c) Determine the minimum force that must be applied to start the body moving up the slope. (8 marks)
