Engineering Mechanics

Engineering Network Engineering BACHELOR OF ENGINEERING TECHNOLOGY PROGRAMME SEMESTER 1, 2017 EXAMINATION SUBJECT: Engineering Mechanics CODE: ENGG MG5002 SHEET: 1 of 8 SEMESTER: 1 DATE: Monday 26th June 2017 DURATION: 3 Hours Assessment breakdown: This examination 50% Other 50% This examination has 15 questions The total mark for this examination is 100 INSTRUCTIONS TO CANDIDATES 10 minutes reading time will be allowed before commencement of this examination. This is a closed book examination. Answer ALL questions. Non programmable electronic calculators are permitted. The following texts are permitted: None Upon completion of this examination, ensure that on the front page of your answer book you have ticked the questions that you have completed, and also recorded your student ID number, subject and subject code. Before handing in your script, ensure that your student ID number is on the top of any loose pages, and that all pages are attached and in the correct order. Show all workings for full marks. Workings can include sketches. Formulas Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 2 of 8 Question 1 (4 marks) What is the resultant force on the ring (the three forces are concurrent and co-planar). Provide both the magnitude of the resultant force, its direction and its angle measured from the x-axis. Question 2 (6 marks) A 30 mm diameter solid steel rod has an original length 1.2 m. It is placed under a tensile stress of 220 MPa. Assuming steel has a Young’s Modulus, E = 200 GPa, answer the following: (a) Calculate the strain, and how much the rod lengthens by in mm (2 marks) (b) Calculate the tension force, F (2 marks) (c) Under the same calculated tension force, F, what would be the required (2 marks) minimum diameter of the rod in order to limit the tensile stress to 160 MPa. Question 3 (5 marks) Calculate the beam reactions at A and B. Assume that the beam itself has no mass. (3 marks) Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 3 of 8 Question 4 (10 marks) Calculate the shear forces and bending moments, and draw the shear force and bending moment diagrams showing all significant values. Then sketch the deflected shape. Note the reactions are provided. Question 5 (10 marks) Consider the truss frame (the reactions have been calculated for you), and calculate the forces in the labelled members, a to g, and for each state compression or tension (use the methods most convenient to you). Question 6 (8 marks) Find the distance to the centroid of the shape below, in both the x and the y directions and measured from the origin, O. Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 4 of 8 Question 7 (10 marks) A train engine of 600 tonnes ascends a slope of 1 in 75, increasing its speed from 30 kph to 70 kph over a distance of 300 m. The tractive resistance to motion is 150 N/tonne. Calculate the Tractive Effort of the engine, and from this calculate the power developed at maximum speed. Question 8 (4 marks) (a) Determine the shear force, V, required to cut through the steel plate, along (2 marks) the dotted line. Assume the shear strength of the steel is 240 MPa. The plate is 5 mm thick. (b) Calculate the force F, if the shear stress in the bolts is 80 MPa, and the (2 marks) bolt diameters are 25 mm. Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 5 of 8 Question 9 (6 marks) A 9800 kg railroad car traveling at a velocity of 12 m/s strikes a second boxcar that is moving at 4 m/s in the same direction . If the two cars stick together and move off with a velocity of 9 m/s, what is the mass of the second boxcar? Question 10 (6 marks) What is the force F required to (a) push the block, and (b) pull the block, so that the block moves at constant velocity. The mass of the block is 30 kg, and the coefficient of friction between the surfaces is µ = 0.35, and the Friction force, Fr = µFN Question 11 (6 marks) A cannon ball is fired out the mouth of a cannon, with an initial velocity of V0 = 200 m/s and at an angle of ϴ = 45 degrees to the horizontal. What will be the maximum height, h, the cannon ball attains, the total flight time, and the range of the cannon ball? Ignore air resistance. Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 6 of 8 Question 12 (10 marks) A speeding car passes a stationary police motorcycle. At the moment the car passes the police motorcycle its speed is 110 kph. The car has a constant acceleration of 0.8 ms-2. After a delay of 5 seconds, the police motorcyle begins to give chase, accelerating at 4 ms-2. How long does it take for the police motorcycle to catch up to the speeding car? And when this happens, what is the velocity of the motorcycle and the velocity of the car? Question 13 (2 marks) The steel oil tank below has dimensions of 1830 mm x 610 mm x 1220 mm. If it completely filled, calculate the total weight of oil contained, if the Specific Gravity of oil is 0.85. Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 7 of 8 Question 14 (5 marks) The swimming pool below is filled with water to a constant depth of 2.1 m. (a) What is the water pressure at the bottom of the pool? (b) Calculate the resultant force from water pressure on the bottom surface (2 marks) of the pool. Where does this force act? (c) Calculate the resultant force from water pressure on one of the 30 m long (2 marks) side walls of the pool. Where does this force act? (1 mark) Question 15 (8 marks) Consider the system below. The Effort required to lift the Load of 294.3 N is 110 N. For every 50 mm the Load moves, the Effort moves upwards 165 mm. (a) Calculate the velocity ratio, VR (1 mark) (b) Calculate the mechanical advantage, MA (1 mark) (c) Calculate the work done directly on the load if it is lifted 100 mm (1 mark) (d) Calculate the distance moved by the effort when the load moves 100 mm (1 mark) (e) Calculate the work done by the effort in causing the load to move 100 mm. (1 mark) (f) What is the efficiency, η, of the system? (2 marks) (g) Why is the system not 100% efficient i.e. why do you think that not all of the work done by the effort goes into lifting the mass? (1 mark) Semester 1, 2017 Examination ENGG MG5002 Engineering Mechanics Page 8 of 8