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Cork Institute of Technology
Bachelor of Engineering in Mechanical Engineering – Stage 1
(NFQ Level 7)
Autumn 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
1 (a) A bracket is exposed to two forces as shown. Find the magnitude and direction of the resultant force. What force is required to keep this bracket in equilibrium? (8 marks)
(b) A weight of 200N is lifted by two ropes connected to the same point on the load. The tension in the rope on the right is 119N and this rope makes an angle of 40 o^ to the vertical. Determine the tension in the other rope required for equilibrium and determine the angle it makes to the vertical. (12 marks)
2.(a) A car is initially moving at 6m/s and with a uniform acceleration of 2.4m/s^2. Find its velocity after 6 seconds and the distance travelled in that time. (5 marks)
(b) A train leaves station A and accelerates from rest at a uniform rate of 3 m/s2. It reaches a maximum speed of 31 m/s. Approaching station B it slows down at a uniform rate of 2. m/s2 and stops at station B. Calculate the time to travel from station A to station B which is a distance of 1670m. (15 marks)
3.(a) A car exerts a constant tractive effort of 2500 N. The mass of the car is 1.1 tonne and the rolling resistance is 220 N. Calculate the acceleration. (5 marks)
(b) A car of mass 1 tonne draws a trailer of mass 0.9 tonne up an incline of 10o. If the car engine produces a tractive effort of 5kN and there is a resistance to motion of 90N per tonne on both the car and the trailer, calculate the acceleration and the tension force in the tow bar. (15 marks)
4 The triangular framework shown is loaded by a vertical force of 1 kN at joint ABD. Determine graphically the magnitude and nature of the force in each member and the vertical support reactions at the pin-joints ADC and BCD. ( marks)
5 Define elastic limit, yield strength and ultimate tensile strength. (5 marks) A copper wire 1.6mm diameter and 4m long extends 1.7mm when carrying a load of 98 N. Find (i) the stress and the strain in the wire at this load, (ii) the modulus of elasticity of the copper, (iii) the factor of safety if the ultimate tensile strength of the copper is 220MN/m^2.
