UNIVERSITY OF BRITISH COLUMBIA 2017/2018 WINTER SESSION MARCH EXAMINATION PHYSICS 170 MECHANICS I 8:00 pm to 9:00 pm, Tuesday, March 6, 2018 MARKS This exam counts for a total of 30 marks towards your Final Grade for the course. The exam consists of 2 questions. The questions are worth the same number of marks. Write all work to be marked in the Answer Booklet provided. NUMERICAL ANSWERS Write numerical answers to three significant figures with units. 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 March Exam: 8:00 pm to 9:00 pm, Tuesday, March 6, 2018 QUESTION 1 The diagram below shows a rigid body AB acted on by a - 600 k N force at E and by a couple moment M= (600 ] + 1200 k) N · m where ] and k are the usual Cartesian unit vectors. AB is held in equilibrium by cables BC and BD and by a ball-and-socket joint at A. The weight of the AB may be neglected. a) Draw a large, clear free-body diagram for AB. b) Determine Cartesian component force equations of equilibrium for AB. c) Determine a vector moment equation of equilibrium in determinant form for AB. d) Determine Cartesian component moment equations of equilibrium for AB. e) Determine numerical values for the Cartesian components of reaction at A and the tension in the cables. 6 -31 2 m Ce 2 m ED B E A 0 3 m -3 m 3 m V 600 N
PHYSICS 170 MECHANICS I March Exam: 8:00 pm to 9:00 pm, Tuesday, March 6, 2018 QUESTION 2 The diagram below shows a uniform wheel and a uniform block on a rough horizontal surface. A cord wrapped around the wheel is attached to the top of the block. A vertical force P acts on the wheel as shown. The wheel weighs 30 lb. The block weighs 50 lb. The weight of the cord may be neglected. The coefficient of static friction at Bis 0.2. The coefficient of static friction between the block and the surface is 0.4. Impending sliding occurs at B. a) Draw large, clear free-body diagrams for the wheel and for the block. b) Determine equations of equilibrium for the wheel and for the block. c) Determine numerical values for P, the tension in the cord, and all friction and normal forces. d) Determine that the block does not slide and does not tip. P 1.5 ft A C 3 ft 1.5 ft B D