EF 151 Exam 3 - Spring, 2017 Page 1 Copy 1 Name: Section: Before the Exam Starts: 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. Instructions and Guidelines for the Exam: Completely color in the dots for multiple choice questions. Write your final answers in the boxes provided for numerical problems 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 At the end of the Exam: 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. Time 11:10 12:40 2:10 Room 102 216 217 A102 A216 A217 Rachel Breanna Tayler B102 B216 B217 Rachel Breanna Tayler C102 C216 C217 Rachel Breanna Tayler
EF 151 Exam 3 - Spring, 2017 Page 2 Copy 1 [DO NOT WRITE ON THIS PAGE]
EF 151 Exam 3 - Spring, 2017 Page 3 Copy 1 Name: Section: 1. (1 pt each) Enter your EXAM ID from your seating label. If you don t know your exam ID, enter 000. 0 1 2 3 4 5 6 7 8 9 Digit #1 Digit #2 Digit #3 4. (2 pt) The area under a force-distance graph gives the following information: Momentum Kinetic Energy Impulse Work 5. (2 pts) A scooter that is 67% efficient is designed to consume 640 J of energy. How much energy is available for the scooter to do work? 429 J 640 J 955 J 1280 J 6. (5 pt) Breanna (110 lb) is lifting weights at the gym. She lifts a 80 lb weight straight above her head (height of 6 ft) in 0.45 s. How much power was required to lift the weight? 7. (15 pt) Mabel is riding in a cart (W total = 23 lb). The cart is subject to a variable force, as shown. If the cart starts with a speed of 8 ft/s, how fast is the cart going after 15 feet? Force 19 lb 30 ft Distance
EF 151 Exam 3 - Spring, 2017 Page 4 Copy 1 8. (2 pts) Conservation of momentum applies if: We only look at the initial and final position of a system The sum of the internal forces on the system is zero The sum of the external forces on the system is equal to zero We do not care about the time required to move between two points 9. (2 pts) Mabel drops her toy ball straight down on the ground. Before the collision, the ball has a speed of 7 m/s. After the collision the ball has a speed of 3 m/s. What is the coefficient of restitution between the ball and the ground? 0 0.429 1 2.33 10. (5 pts) A 5 gram bullet is fired horizontally with a velocity of +965 m/s at a 7.0 kg stationary block of wood resting on a table. What is the velocity of the bullet after the collision if it imbeds in the wood block? 11. (15 pts) Honey pushes her treats in a cart (W total = 30 N) with a varying force. She starts from rest with a starting push force of 4 N that linearly increases to a push force, P, over 5 seconds. She then linearly decreases her push force to zero over the next 10 seconds, ending at a speed of 22 m/s. How hard is Honey pushing at 5 sec?
EF 151 Exam 3 - Spring, 2017 Page 5 Copy 1 12. (2 pts) Where does the datum HAVE TO BE set for gravitation potential energy? Lowest Point Undeformed position Initial position Anywhere 13. (2 pts) Which of the following is not a unit of energy? Nm kg m2 s 2 Joule 14. (5 pts) A 10 lb bowling ball is launched from rest into the air by spring energy. If the spring (k = 550 lb/ft) is deflected 2.4 inches initially, what is the maximum height the bowling ball will reach above the deflected length of the spring? Joule s 15. (16 pts) Honey rides on a sled down a hill as shown. What is the kinetic coefficient of friction between the sled and the hill? (FBD Required) Point A VA = 4 ft/s H = 8 ft Point B VB = 17 ft/s L = 35 ft
EF 151 Exam 3 - Spring, 2017 Page 6 Copy 1 16. (2 pts) A ball is dropped from a height of 100 feet. When it hits the ground, it does not bounce back into the air. What type of collision best explains this situation? Perfectly inelastic Inelastic Perfectly elastic Explosion 17. (2 pts) The same ball is thrown on a trajectory path as shown to the right. What can you say about the x-velocity of the ball AFTER the collision with the ground? Zero Same as x- velocity before collision Same as y- velocity after collision Cannot determine y x 18. (5 pts) A 250 gram marshmallow gun has a recoil velocity of +0.4 m/s when shooting a 7 gram marshmallow. What was the velocity of the marshmallow when shot from the marshmallow gun? 19. (15 pts) Mabel is running towards a moving soccer ball as shown. Mabel and the soccer ball collide. If the coefficient of restitution for the collision is e = 0.60, what is Mabel s velocity after the collision? V m = 9 ft/s V h = 27 ft/s Mabel Wm = 18 lb Honey W h = 0.8 lb