EF 151 Exam #3 - Spring, 2016

Transcription

1 Name: Section: Instructions: Sit in assigned seat; failure to sit in assigned seat results in a 0 for the eam. Put name and section on your eam. 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 boes proided If you finish with less than 5 minutes remaining, please stay seated until the eam is oer. Stop work immediately when time is oer; working after time is oer results in an automatic point deduction Turn in your equation sheet with your eamination. Pass eams to the aisle; stay seated until all eams are collected. Guidelines: Assume 3 significant figures for all gien numbers unless otherwise stated Show all of your work no work, no credit Include units for all answers and directions for all ectors 11:10 12:40 2: A102 Rachel B102 Rachel C102 Rachel A216 Connor B216 Connor C216 Connor A217 Tayler B217 Tayler C217 Tayler

2 1. (2 pt) Print your NetID neatly in capital letters. Your NetID is the first part of your official UT (2 pt) What does the area obtained from a force-displacement graph represent? A. Friction B. Work C. Impulse D. Net force 3. (2 pt) A crate is pushed and sliding to the right as shown in the FBD. What are the signs for the work done by each of the indiidual forces? F 1 F 2 F 3 F 4 A B C D E F (2 pt) How would you calculate the force required to stretch a spring? A. F = ½ k 2 B. F = m a C. F = k D. F = ½ m 2 5. (2 pt) What does the impulse applied to an object equate to? A. Change in kinetic energy B. Change in graitational potential energy C. Change in elocity D. Change in momentum 6. (2 pt) Which quantity does not affect an object s kinetic energy? A. weight B. speed C. direction of motion D. mass

3 7. (2 pt) A ball is rolling with negligible frictional drag along a loop-the-loop track. How does the ball s speed at point P (rolling down the ramp) compare to its speed at point Q (at the top of the loop)? Both points are the same distance aboe the ground. A. More information is needed B. V P = V Q C. V P > V Q D. V P < V Q 8. (2 pt) Consider two carts of masses m and 2m, at rest on an air track. If you push one cart for 3s and then the other cart for the same length of time, eerting equal force on each, the momentum of the light cart is the momentum of the heay cart. A. Four times B. Twice C. Equal to D. One-half E. One-quarter 9. (2 pt) If all three collisions in the figure shown here are perfectly inelastic, which bring(s) the car on the left to a halt? A. I B. II C. III D. I, II E. I, III F. II, III G. I, II, III II I III m m m Very massie wall 2m 0.5 m 10. (2 pt) A basketball dropped (from rest) from a height of 1.0 meter strikes the earth and returns to a height of 1.0 meter. The collision between the basketball and the earth is: A. Perfectly elastic B. Inelastic C. Perfectly inelastic D. Eplosie

4 11. (5 pt) Two objects collide in a perfectly elastic collision. The elocity of the 5 kg object after the collision is +5 m/s. What is the elocity of the 3 kg object after the collision? HINT: single calculation. 3 kg 17 m/s 31 m/s 5 kg 12. (5 pt) A crane lifts a weight. The power input to the crane is 1200 W and it is 75% efficient. How much work can the crane do in 5 seconds? HINT: single calculation. 13. (5 pt) A basketball bounces as shown with e=0.6. What is the y component of the ball s elocity ( y) before the bounce? HINT: single calculation. y y' = 5 ft/s ' = 18 ft/s 14. (5 pt) Two balls collide as shown with e=0.6. What is the y component of ball A s elocity after the collision? HINT: single calculation. A = 13 ft/s W A = 12 lb 10 A y B 25 B = 21 ft/s W B = 16 lb

5 15. (15 pt) A 42 lb object is pushed with a ariable force as shown in the F s t diagram. If the object starts with a speed of 4 ft/s, what is the elocity of the object after 7 seconds? F (lb) t (s) 16. (15 pt) Mabel the dog jumps onto a raft. Assuming the dog and raft stay together, what is their final elocity (magnitude and direction)? 6 ft/s y 13 ft/s 15 lb 5 lb

6 17. (15 pt) Professor Schleter sits under a bucket of Hi-C fruit punch. Dr. McCord uses a spring to shoot a ball straight up at the bucket. The ball needs to hit the bucket with a speed of 11 ft/s to make the April Fool s prank a success. How far does Dr. McCord need to compress the spring for the ball to hit the bucket with the required speed? 20 ft 0.7 lb Unstretched spring k = 130 lb/ft 18. (15 pt) The JST Rollercoaster firm is designing a ride that will start from rest at a base station. The top of the first hill will hae a height of 34 m aboe the base. While going up the first hill watts of power are applied in 2.0 seconds. The cars on the ride hae a total mass of 7500 kg and encounter losses of joules while going up the hill. What is the speed of the ride at the top of the hill?