UNIVERSITY OF BRITISH COLUMBIA 2019/2020 WINTER SESSION MARCH EXAMINATION PHYSICS 170 MECHANICS I 6:00 pm to 7:00 pm, Thursday, March 12, 2020 MARKS This exam counts for a total of 30 marks towards your Final Grade for the course. The exam consists of 2 questions. Each question is worth 15 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: 6:00 pm to 7:00 pm Thursday March 12 2020 QUESTION 1 (15 marks) The diagram below shows a rigid body acted on by a 400 N force in the direction shown and by a couple moment M = (-600]+ 720k)N·m where ] and k are the usual Cartesian unit vectors. The body is held in equilibrium by a ball-and-socket joint at D and by cables attached to B and to C. The weight of the body may be neglected. a) Draw a large, clear free-body diagram for the body. (3 marks) b) Determine Cartesian component force equations of equilibrium for the body. (4 marks) c) Determine Cartesian component moment equations of equilibrium for the body. (5 marks) d) Determine numerical values for the Cartesian components of reaction at the ball-and-socket joint and for the magnitudes of the forces exerted by the cables. (3 marks) B 12 Z 3 m ) 6 m C 2 m D A 1 30° 400 N
PHYSICS 170 MECHANICS I March Exam: 6:00 pm to 7:00 pm Thursday March 12 2020 QUESTION 2 (15 marks) The diagram below shows a uniform cylinder with weight 80 lb resting on the horizontal ground and against a vertical wall. A horizontal force P and a force Q act on the cylinder as shown where P = 180 lb and Q = 30 lb. Q is tangent to the cylinder at C and makes an angle of 50 degrees with the vertical. The cylinder is held in equilibrium by normal and friction forces. The magnitude of the normal force at A is 190 lb. a) Draw a large, clear free-body diagram for the cylinder. (4 marks) b) Determine Cartesian component equations of equilibrium for the cylinder. (4 marks) c) Determine numerical values for the magnitudes of the friction forces at A and B and for the normal force at B. (4 marks) d) The coefficients of sliding friction at A and B are both 0.2. Determine whether or not the cylinder is in impending motion. (3 marks) 10 0 50 C 3 ft A 1 ft 0 P B