THE UNIVERSITY OF BRITISH COLUMBIA 2011/2012 WINTER SESSION SESSIONAL EXAMINATIONS PHYSICS 170 MECHANICS I 3:30 pm to 6:00 pm, Wednesday, December 7, 2011 MARKS This exam counts for a total of 60 marks towards your Final Grade for the course. The exam consists of 4 questions worth a total of 70 marks. Questions 1 and 2 are each worth 20 marks. Questions 3 and 4 are each worth 15 marks. Write all work to be marked in the Answer Booklets provided. NUMERICAL ANSWERS You must give numerical answers correctly to three figures and with correct units to get any marks for your numerical answers. No marks are given 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 Final Exam: 3:30 pm to 6:00 pm, Wednesday, December 7, 2011 QUESTION 1 (20 marks) The diagram below shows a uniform circular door in equilibrium in the horizontal plane. The door weighs 50 lb; its centre of gravity is at G; its radius is 3 ft. The door is acted upon by a couple moment M = (607+80]+100k) lb -ft at G. The door is held in equilibrium by a frictionless hinge at A and by a strut CB. The angle 0 = 40Ā°. a) Draw a large, clear free-body diagram for the door. Show also the Cartesian unit vectors and the numerical values of the coordinates of B, C and G. (4 marks) b) Express the force of the strut CB on the door as a Cartesian vector. (2 marks) c) Determine the three Cartesian component force equations of equilibrium for the door. (3 marks) d) Determine the vector moment equation of equilibrium for the door. (4 marks) e) Determine the three Cartesian component moment equations of equilibrium for the door. (3 marks) f) Solve the six Cartesian component equations of equilibrium to determine the Cartesian components of reaction at the hinge A and the magnitude of the force of the strut CB on the door. (4 marks) Z A G X 3 ft 0 y B 3 ft C
PHYSICS 170 MECHANICS I Final Exam: 3:30 pm to 6:00 pm, Wednesday, December 7, 2011 QUESTION 2 (20 marks) In the diagram below, particle C of mass 2 kg travels along the path described by r = (0.6 sin0) m due to rotation of the slotted arm guide OA. Motion is in the vertical plane; 0 is the angle OA makes with the horizontal. In addition to the force of the slotted arm guide, particle C is acted on by gravity, the compressed spring, a normal force, and a friction force opposing its motion along the