Remove this sheet AFTER the exam starts and place your name and section on the next page.

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1 EF 151 Final Exam, Spring, 2014 Page 1 of 10 Remove this sheet AFTER the exam starts and place your name and section on the next page. Instructions: Guidelines: Do not open the test until you are told to do so. Write your final answer in the box 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; pass exams to the aisle; stay seated until all exams are collected. 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 Include directions for all vectors

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3 EF 151 Final Exam, Spring, 2014 Page 3 of 10 Name: Section: 1. (1 pt) Which equation for the instantaneous velocity of an object undergoing constant, non-zero acceleration is NOT true? s 2s 2 a. v b. v v 0 at c. v v0 d. v 2as v 0 t t 2. (1 pt) Vector A is added to vector B. Under what conditions does the resultant vector A + B have SMALLEST magnitude? a. When A and B are parallel and in the same direction. b. When A and B are parallel and in the opposite direction. c. When A and B are perpendicular. d. The magnitude of A + B does not depend on the directions of A and B. 3. (1 pt) A spherical balloon has a volume of 1 ft 3. The balloon is inflated so that it has twice its original diameter. What is the volume of the inflated balloon? 4 a. 2 ft 3 b. 4 ft 3 c. 8 ft 3 3 d. (2 ft) 3 4. (1 pt) When we looked at including drag in projectile motion, what assumption was made when calculating the change in position over a small change in time? a. No horizontal acceleration b. No vertical acceleration c. Constant velocity d. Constant acceleration e. No drag 5. (1 pt) A cart on wheels is rolling at a constant velocity. Which statement MUST be true? a. F friction = 0 b. F net = 0 c. F friction = µ k*n d. F friction = µ s*n 6. (1 pt) Which FBD is correct for a person throwing a book up and to the right without sliding on the support surface? (Person isolated, before releasing the book, W=weight, N=normal, P=push, F=friction). A B C D 7. (3 pt) Describe Newton s laws of motion with a word, short phrase, or equation. 1 st : 2 nd : 3 rd :

4 EF 151 Final Exam, Spring, 2014 Page 4 of (1 pt) How was the actual exit velocity determined in the roller coaster project (ball bearing in the tube)? a. Cons. of energy b. Cons. of momentum c. Projectile motion d. F = ma 9. (1 pt) What is the value for the coefficient of restitution for a perfectly elastic collision? a. 0 b. Between 0 and 1 c. 1 d. Greater than 1 d. Depends upon the velocities 10. (1 pt) When is the angular momentum about the axis of rotation of a system not conserved? a. When there is a net force parallel to the axis of rotation. b. When there is a net torque parallel to the axis of rotation. c. When there is a net torque perpendicular to the axis of rotation. d. Where there is friction between two objects that are both in the system. 11. (1 pt) If a ball rolling on an open track is released from rest at the position shown, will it make it through the loop without leaving the track? a. Yes b. No c. Depends on the radius d. Depends on the friction 12. (1 pt) A billiard ball (I=0.4mr 2, m=0.1 kg, r=2.4 cm) and a solid cylinder (I=0.5mr 2, m=3 kg, r=1.8 cm) start from rest and roll without slipping down an incline. If there are negligible losses, which one reaches the bottom last? a. billiard ball b. cylinder c. same time d. not enough information 13. (1 pt) A car is traveling around a circular track as shown and is speeding up. Which vector best represents the direction of the car s total acceleration? H A B 14. (1 pt) A disk is spinning with a speed of 600 rpm as shown. How would you represent its angular velocity vector? a. +600i rpm b. +600j rpm y c. +600k rpm d. -600i rpm e. -600j rpm f. -600k rpm x G F E D C z

5 EF 151 Final Exam, Spring, 2014 Page 5 of (7 pts) Determine the magnitude and direction of A - B. 16. (7 pts) Donny Tyndall flies 250 miles at 30 N of W, then flies 400 miles at 18 W of S, and then flies 175 miles due east. How far must he fly to return to his starting point?

6 EF 151 Final Exam, Spring, 2014 Page 6 of (7 pts) An object experiencing constant 1D acceleration starts with a velocity of -14 m/s at position 7.0 m. After 15 seconds it is at position 42 m. What was its acceleration during this time? 18. (7 pts) Determine the launch speed (pt A) required to hit the stick man on top of the head (pt B). A B

7 EF 151 Final Exam, Spring, 2014 Page 7 of (7 pts) A 2800 lb van (C d = 0.05 lb-s 2 /ft 2 ) is pulling a trailer of an unknown weight. The trailer s wheels roll freely, the drive (traction) force for the van is 800 lb, and the drag force of the air on the van is given by F drag = C dv 2. What is the magnitude of the force in the connection between the van and the trailer when it is going 30 mph (44 ft/s) and its acceleration is 2.5 ft/s 2? (FBD = KD required. Hint: isolate the van) 20. (7 pts) A 5 lb easter basket is sliding UP a ramp. Determine the magnitude of the acceleration at the instant shown. (FBD = KD required) 10 ft/s µ s = 0.55 µ k =

8 EF 151 Final Exam, Spring, 2014 Page 8 of (7 pts) A spring (k = 40 lb/ft) is used to shoot a 22 lb box full of portfolios up an incline. The box starts from rest on a compressed spring. It slides a total distance of 7.9 ft with a constant friction force of 6.76 lb. Its speed at that point is 6.0 ft/s. The box is not attached to the spring. What distance was the spring initially compressed? 6.0 ft/s (7 pts) A 15 kg object with an initial velocity of 7.0 m/s has a varying force F (as shown in the graph) applied to it while moving in a straight line on a horizontal surface. Determine the speed of the object after 10 seconds. 60 N 25 N F 4 sec 10 sec t

9 EF 151 Final Exam, Spring, 2014 Page 9 of (7 pts) Two hockey pucks sliding on ice collide as shown. The coefficient of restitution between the pucks is What is the velocity (speed AND direction) of puck A after the collision? 24. (7 pts) A Rube-Goldberg device uses an electric motor that is 61% efficient to spin a solid sphere (150g, 3 cm radius) about its center axis. How much energy must be input into the motor if the sphere starts from rest and ends with a speed of 750 rpm? (I sphere = 2/5mr 2 )

10 EF 151 Final Exam, Spring, 2014 Page 10 of (7 pts) A bus starts from rest and increases its speed at a constant rate on a flat, circular track. After it has completed one lap its angular velocity is 0.42 rad/s and its total acceleration is 15 m/s 2. What is the radius of the track? 26. (7 pts) A 1.0 lb glob of mud is thrown at a stationary vertical plank hanging from a frictionless support (A) as shown (I A = 0.22 slug-ft 2 ). The mud sticks to the plank and the combination swings CCW about axis A. What is the rotational speed of the combination the instant it starts rotating?