EF 151 Exam #2 - Spring, 2016 Page 1 of 6 Name: Section: Instructions: Sit in assigned seat; failure to sit in assigned seat results in a 0 for the exam. Put name and section on your exam. Put seating label on your equation sheet. Do not open the test until you are told to do so. Write your final answers in the boxes provided If you finish with less than 5 minutes remaining, please stay seated until the exam is over. Stop work immediately when time is over; working after time is over results in an automatic point deduction Turn in your equation sheet with your examination. Pass exams to the aisle; stay seated until all exams are collected. Guidelines: Assume 3 significant figures for all given numbers unless otherwise stated Show all of your work no work, no credit Include units for all answers and directions for all vectors 11:10 12:40 2:10 102 216 217 A102 Rachel B102 Rachel C102 Rachel A216 Connor B216 Connor C216 Connor A217 Tayler B217 Tayler C217 Tayler
EF 151 Exam #2 - Spring, 2016 Page 2 of 6 1. (2 pts) A dog weighs 29 lb on Mars. gmars = 12.2 ft/s 2. What is the dog s mass on Earth? A. 0.90 lb B. 2.4 lb C. 29 lb D. 77 lb E. 0.90 slugs F. 2.4 slugs G. 29 slugs H. 77 slugs 2. (2 pts) What is the magnitude of the drag force on a 16.1 lb falling object when it reaches terminal velocity? A. 0 B. 0.5 lb C. 2.0 lb D. 16.1 lb E. 32.2 lb 3. (2 pts) A moving sidewalk has a velocity of +7 m/s. Tayler is walking on the sidewalk with a velocity of +2 m/s relative to the sidewalk. A dog is running beside the sidewalk with a velocity of -3 m/s. What it the velocity of the dog with respect to Tayler? A. +12 m/s B. +8 m/s C. +6 m/s D. -6 m/s E. -8 m/s F. -12 m/s 10 lb P μs = 0.8 μk = 0.6 4. (2 pts) Determine the friction force if P = 5 lbs and the block is not sliding. 5. (2 pts) Determine the friction force if P is such that the block is getting ready to start sliding to the left. 6. (2 pts) Determine the friction force if P = 12 lbs and the block is sliding to the left.
EF 151 Exam #2 - Spring, 2016 Page 3 of 6 Draw a free body diagram and kinetic diagram for each of the following situations. Be sure to clearly label all components. Do not include zero magnitude vectors. You must specify a coordinate system for each system. 7. (4 pts) A box being pushed up a rough 45 incline. The box s speed is increasing and the push force is horizontal. Isolate the box. 8. (4 pts) A basketball after it is shot up and to the right. The ball has a velocity of 5 m/s and an angle of 45 above horizontal. Include air resistance. 9. (4 pts) A boy sitting in wagon rolling on level ground. Isolate the boy. The wagon is moving to the right and slowing down.
EF 151 Exam #2 - Spring, 2016 Page 4 of 6 10. (10 pts) An object starts at a position of (8i 5j )ft with an initial velocity of (16i + 7j )ft/s and a constant acceleration of ( 3i )ft/s 2. What is the object s position (i, j notation) when it reaches its maximum in the x direction? 11. (10 pts) A golf ball is dropped out of a helicopter flying very high. What is the ball s speed when it hits the ground? ρair = 1.23 kg/m 3, Cd = 0.32, radius = 21.5 mm, mass = 46 grams.
EF 151 Exam #2 - Spring, 2016 Page 5 of 6 12. (14 pts) A ball is thrown from a 79m high cliff as shown. It takes 2.4 seconds to hit the ground. Determine the horizontal distance (d) it travels. (Assume ideal projectile motion) 79 m 13 V 0 d 13. (14 pts) A 1200 lb tractor with a tractive force of 700 lb pulls an 800 lb log up a hill. The friction force between the log and the ground is 320 lb. Determine the tension in the chain between the tractor and the log. (2 FBD = KD required) 10
EF 151 Exam #2 - Spring, 2016 Page 6 of 6 14. (14 pts) A book is being held against the wall as shown and is sliding down at a constant speed of 0.7 m/s. Determine the mass of the book. (FBD required) μ s = 0.7 μ k = 0.5 42 N 60 15. (14 pts) A plane s velocity with respect to the air is 300 mph 40 N of W. The wind is blowing with a velocity of 50 mph 15 E of N. If the flight lasts 2.5 hrs, how far and in what direction did the plane actually fly?