THE UNIVERSITY OF BRITISH COLUMBIA 2015/2016 WINTER SESSION FEBRUARY EXAMINATION PHYSICS 170 MECHANICS I 8:00 pm to 9:00 pm, Tuesday, February 9, 2016 MARKS This exam counts for a total of 20 marks towards your Final Grade for the course. The exam consists of 2 questions. Each question is worth 20 marks. Write all work to be marked in the Answer Booklets provided. NUMERICAL ANSWERS You must write numerical answers correctly to three significant figures and with correct units to get any marks for your numerical answers. No marks are awarded for correctly solving incorrect equations. CALCULATOR You may use a graphing calculator. INFORMATION SHEET You may consult one 8 1/2 inch by 11 inch hand-written double-sided Information Sheet. Your Information Sheet must not contain any sample problems or solutions to sample problems. Put your name and student number on your Information Sheet. You must hand in your Information Sheet with your Answer Booklet in order for your exam to be marked.
PHYSICS 170 MECHANICS I February Exam: 8:00 pm to 9:00 pm, Tuesday, February 9, 2016 QUESTION 1 (20 marks) The diagram below shows a tower AE with cables attached to point A on the tower and to points B, C and D on the xy-plane. The tower is in equilibrium. Point A on the tower is held in equilibrium by tension forces in the three cables and by a 770 lb force directed along the z-axis. a) Draw a large, clear free-body diagram for point A. (5 marks) b) Determine Cartesian component equations of equilibrium for point A. (6 marks) c) Determine the magnitudes of the forces exerted by the cables on point A. (4 marks) d) The force exerted by any cable cannot exceed 500 lb. Determine the largest force that can be directed along the z-axis for point A to remain in equilibrium. (5 marks) Z A 30 ft 10 ft C 10 ft B 15 ft E D 15 ft 12.5 ft x y
PHYSICS 170 MECHANICS I February Exam: 8:00 pm to 9:00 pm, Tuesday, February 9, 2016 QUESTION 2 (20 marks) The diagram below shows a rigid pipe assembly acted upon at point C by a force F with magnitude 80 N and direction as shown, at point A by a force FA =(107 -20]+30k) N, and by a couple moment M= (-207-30]+40k) Nm where 7, j, k are the usual Cartesian unit vectors. a) Draw a large, clear diagram for the pipe assembly showing the forces and the couple moment. (3 marks) b) Determine F as a Cartesian vector. (3 marks) c) Determine the magnitude and coordinate direction angles of FA · (3 marks) The forces and the couple moment shown on the diagram can be replaced by an equivalent resultant force FR acting at point C and a resultant couple moment (MR)c · d) Determine FR as a Cartesian vector. (3 marks) e) Determine (MR)c as a Cartesian vector. (7 marks) f) Are FR and (MR)c a wrench? Explain. (1 mark)