UNIVERSITY OF BRITISH COLUMBIA 2018/2019 WINTER SESSION SESSIONAL EXAMINATION PHYSICS 170 MECHANICS I 12 noon to 2:30 pm, Monday, April 8, 2019 MARKS This exam counts for a total of 60 marks towards your Final Grade for the course. The exam consists of 4 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 Final Exam: 12 noon to 2:30 pm, Monday, April 8, 2019 QUESTION 1 (15 marks) The diagram below shows a rigid body with centre of mass at G held in equilibrium by a ball-and-socket joint at A and by wires BC and BD. The mass of the body is 80 kg. G lies 0.5 m below the xy-plane. The z-axis is vertical. The body is acted upon by a couple moment M = (-4007 + 200k) N ·m at B. a) Draw a large, clear free-body diagram for the body. b) Determine Cartesian component force equations of equilibrium for the body. 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 in the wires. (3 marks) (4 marks) (3 marks) Z 1 ? 2 m C Q D 1 m 2 m 12 1 A ECO x B -y ·G 1 m -1 m £
PHYSICS 170 MECHANICS I Final Exam: 12 noon to 2:30 pm, Monday, April 8, 2019 QUESTION 2 (15 marks) The diagram below shows two triangular blocks A and B. The mass of A is 2 kg. The mass of B is 3 kg. B is on a horizontal surface. The sloped surface of B makes an angle of 40° with the horizontal. The coefficient of kinetic friction between B and the horizontal surface is 0.5. The coefficient of kinetic friction between the two blocks is 0.2. A force P with magnitude 50 N acts horizontally to the right on A. P causes the blocks to accelerate. A and B have different accelerations. a) Draw large, clear free-body diagrams for the blocks. (5 marks) b) Determine Cartesian component equations of motion for the blocks. (6 marks) c) Determine numerical values for the acceleration of each block and for the normal forces. (3 marks) d) Determine the numerical value of the angle the acceleration of A makes with the horizontal. (1 mark) P A B