EF 151 Final Exam, Fall, 2015 Page 3 of 10

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1 EF 151 Final Exam, Fall, 2015 Page 3 of 10 Name: Multiple choice questions: 1 point each 1. The acceleration of gravity in mile/min 2 is: a. 1.69x10-6 mile/min 2 b mile/min 2 c mile/min 2 d. 6.12x10 8 mile/min 2 2. The angle, CCW from the x-axis of the vector (6ıı 4ȷȷ ) is: a. 123 b. 146 c. 304 d n object has a velocity of -3.5m/s and a tangential acceleration of +2.4m/s 2. The object is: a. slowing down b. speeding up c. moving at constant velocity 4. n object s velocity is described by vv = (5tt 2 + 2)ffff/ss The acceleration at t=3sec is: a. 15 ft/s 2 b. 30 ft/s 2 c. 47 ft/s 2 d ft/s 2 5. basketball is dropped from a window and hits the ground 1.6 seconds later. basketball thrown horizontally from the same window will hit the ground in (neglect air resistance): a. < 1.6 seconds b. 1.6 seconds c. > 1.6 seconds Section: 6. person is accelerating at a rate of +2 ft/s 2 with respect to a moving sidewalk that has a constant velocity of +3 ft/s. The acceleration of the person with respect to the ground is: a. -1 ft/s 2 b. 0 ft/s 2 c. +2 ft/s 2 d. +5 ft/s 2 7. person driving a car is slowing down at a rate of 7 ft/s 2. correct FBD of the person, with all forces in the proper direction is: 8. The direction of the drag force from air resistance is: a. in the direction of the acceleration b. in the opposite direction of the acceleration c. in the direction of the velocity d. in the opposite direction of the velocity 9. The amount of work done by the 12 N force going through the 2 m distance is: a. 0 J b. 12 J c. 21 J d. 24 J 2 m 12 N hp of power is required to drive up a hill. What size engine is required if the car is 55% efficient? a. 20 hp b. 24 hp c. 44 hp d. 80 hp e. 98 hp

2 EF 151 Final Exam, Fall, 2015 Page 4 of In a perfectly elastic one-dimensional direct collision the relative velocity between particles: a. stays the same b. changes sign, but not magnitude c. changes magnitude, but not sign d. changes both sign and magnitude 12. In a two-dimensional collision, the velocity component change of a particle along the plane of contact (POC) and line of impact (LOI) is: a. no change along either POC or LOI b. change along POC, but not along LOI c. change along LOI, but not along POC d. change along both POC and LOI 13. The FBD of a person at the top of a moving Ferris wheel is shown. What is the relation between the magnitudes of the forces? a. WW > NN b. WW < NN c. WW = NN N W 15. The distance d used in the parallel axis theorem to calculate the mass moment of inertia about point is: a cm b. 14 cm c. 19 cm 20 d cm CM e. 24 cm f. 38 cm 16. Power can be calculated as: a. ττ φφ b. ττ ωω c. ττ αα 14. The torque of the 10 N force about point is: a. 20 N-m CW 10 N b. 20 N-m CCW c. 35 N-m CW 30 d. 35 N-m CCW e. 40 N-m CW f. 40 N-m CCW g. 55 N-m CW h. 55 N-m CCW

3 EF 151 Final Exam, Fall, 2015 Page 5 of (7 pts) This system of four forces is in equilibrium. What is the magnitude of B? lb 12 lb 55 B 18. (7 pts) n object starts at position (8ıı 14ȷȷ ) ft with an initial velocity of ( 9ıı + 6ȷȷ ) ft/sec and a constant acceleration of (3ıı 4ȷȷ ) ft/s 2. Determine the distance the object is from its starting point at t=4 seconds.

4 EF 151 Final Exam, Fall, 2015 Page 6 of (7 pts) car is moving with an initial velocity, v o. The car accelerates at 1.2 ft/s 2 for 14 seconds reaching a speed of 26 ft/sec. The car then takes 250 ft to slow down to a stop. a. Determine the initial velocity of the car, v o. b. Determine the distance the car traveled in the first 14 seconds. c. Determine the magnitude of the acceleration when the car slows to a stop. 20. (7 pts) ball is thrown as shown, and hits the ground 1.4 seconds later. Determine the horizontal distance x the ball traveled. Neglect air resistance. 4 ft 55 x

5 EF 151 Final Exam, Fall, 2015 Page 7 of (7 pts) Determine the minimum force P to keep the box from sliding down the incline. FBD required µs=0.6 µk=0.4 6 kg 52 P 22. (7 pts) 32 kg tractor is pushing a 14 kg cart as shown. The tractive force from the tractor is 58 N. There is a retarding force on the cart of 8 N. 2 FBD=KD required a. Determine the acceleration of the system. 32 kg 14 kg b. Determine the magnitude of the coupling force between the tractor and the cart.

6 EF 151 Final Exam, Fall, 2015 Page 8 of (7 pts) motorized cart is going down an incline as shown. The motor provides a tractive force of 18 lbs. The cart has a velocity of 2.7 ft/s when it hits the spring. Determine the required spring stiffness to bring the cart to a stop in 0.3 ft. 40 lb (7 pts) Two objects are traveling as shown and collide in a perfectly inelastic collision. Determine the magnitude of the velocity of the combined objects after the collision. 3 kg 10 m/s 4 kg 6 m/s

EF 151 Final Exam, Fall, 2015 Page 9 of 10 25. (7 pts) Two identical objects collide together as shown in a perfectly elastic collision a.

7 EF 151 Final Exam, Fall, 2015 Page 9 of (7 pts) Two identical objects collide together as shown in a perfectly elastic collision a. Determine the velocity of in the x-direction after the collision. y 6 ft/s b. Determine the velocity of B in the x-direction after the collision. B Plane of contact 30 8 ft/s x c. Determine the velocity of in the y-direction after the collision. 26. (7 pts) The monster truck shown consists of four wheels (uniform circular disk) and a body. Each wheel has a mass of 0.6 kg and a radius of 0.15 m. The body has a mass of 1.7 kg. Determine the total kinetic energy of the truck if it is moving at 0.8 m/s.

8 EF 151 Final Exam, Fall, 2015 Page 10 of (7 pts) When the mass is released and is accelerating, the tension in the rope holding the hanging mass is measured to be 9.2 N. Determine the mass, m. (2 FBD = KD required) solid cylinder 8 kg m 28. (7 pts) 15 lb force is applied to a 3 lb board that is hanging from a hinge at point. a. Determine the magnitude of the torque about point. 15 lb 40 2 ft 0.5 ft b. Determine the mass moment of inertia of the board about point. c. Determine the angular acceleration about point.

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

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