Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 1 Physics 125 Fall 2006: Exam #2 Form #1 Please print your name:_________________________________________ Please list your discussion section number:_________________________ Please list your discussion instructor:______________________________ Instructions • Fill in your name above. • Each exam will have a different version number which will need to be written in the area of the scantron marked “Form”. • Record all your answers on the answer sheet provided. • This will be a 1.5 hour, closed book exam. The exam includes 20 questions. • You may use TWO 3x5 note cards (1 old + 1 new) containing information you think might be useful. You can write on both sides of the card if you like. • This is a closed-book exam. You may use a calculator which is for numerical calculations only and not to refer to stored information. • There is only ONE correct answer for each multiple-choice question. No partial credit will be awarded. • You will be asked to show your University student ID card when you turn in your exam. ID checked by:___________________________________ Discussion section reminder: Section 003 TUE/THUR 08:00-09:00 Andrew Tomasch Section 004 TUE/THUR 09:00-10:00 Andrew Tomasch Section 005 TUE/THUR 10:00-11:00 Andrew Tomasch Section 006 TUE/THUR 11:00-12:00 Gus Evrard Section 007 TUE/THUR 13:00-14:00 Gus Evrard Section 008 TUE/THUR 14:00-15:00 Gus Evrard Section 009 TUE/THUR 14:00-15:00 Andrew Tomasch Section 010 TUE/THUR 15:00-16:00 Andrew Tomasch Section 011 TUE/THUR 16:00-17:00 Andrew Tomasch Section 012 TUE/THUR 12:00-13:00 Sa-Lin Bernstein Section 016 TUE/THUR 11:30-13:00 Arthur Cole Section 017 TUE/THUR 13:00-14:30 Arthur Cole Section 018 TUE/THUR 08:00-09:00 Arthur Cole Section 019 TUE/THUR 09:00-10:00 Sa-Lin Bernstein Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 2 1. You drop an egg from rest with no air resistance. As it falls, A) its mechanical energy is conserved, but its momentum is not conserved. B) both its momentum and its mechanical energy are conserved. C) only its momentum is conserved. D) neither its mechanical energy nor its momentum is conserved. E) only its kinetic energy is conserved. 2. A plane is traveling at 200 m/s following the arc of a vertical circle of radius R. At the top of its path, the passengers experience “weightlessness.” To one significant figure, what is the value of R? A) 40000 m B) 2000 m C) 4000 m D) 1000 m E) 200 m Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 3 3. A disk starts from rest and has a constant angular acceleration. If it takes time T to make its first revolution, in time 2T (starting from rest) the disk will make A) 4 revolutions. B) 16 revolutions. C) 8 revolutions. D) 2 revolutions. E) 2 revolutions. 4. A cue ball (mass = 0.165 kg) is at rest on a frictionless pool table. The ball is hit dead center by a pool stick, which applies an impulse of +1.25 N·s to the ball. The ball then slides along the table and makes an elastic head-on collision with a second ball of equal mass that is initially at rest. Find the velocity of the second ball just after it is struck. A) 7.58 m/s B) 7.00 m/s C) 4.22 m/s D) 6.91 m/s E) 5.73 m/s Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 4 5. Which of the following is physically impossible? A) The chance of a light car safely rounding an unbanked curve on an icy road is the same as that for a heavier car (assuming that all other factors are the same). B) A car is accelerating around a turn at constant speed. C) A car hits a garbage truck, exerting a force equal to the force the garbage truck exerts on it. D) A car is at rest with zero acceleration but has forces acting on it. E) A car rounds a turn with a constant acceleration. 6. A 20-N force is applied at an angle of 60 o to the horizontal to pull a block across a frictional surface at a constant speed for a displacement of 5.0 m to the right. Which of the following statements is (are) true? I. The kinetic friction does −50 J of work. II. The normal force and the gravitational force do no work. III. The applied force does +50 J of work. A) I, II, and III. B) III only. C) II and III. D) I only. E) II only. F applied =20 N 60 o Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 5 7. Two satellites, A and B, are in different circular orbits about the earth. The orbital speed of satellite A is 2 times that of satellite B. Find the ratio of the orbit radius of satellite A to that of satellite B. A) 4 B) 1/4 C) 2 D) 1 E) 1/2 8. A net external force acts on a particle. The net force is not zero. This is sufficient information to conclude that I. the velocity of the particle changes. II. the kinetic energy of the particle changes. III. the speed of the particle changes. A) I and II. B) I only. C) II only. D) I, II, and III. E) III only. Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 6 9. I’m going to push on two vehicles which roll without friction. I will push for 5 seconds with a total force of 500 N. One vehicle is a car which has a mass of 910 kg, the other is a minivan which has a mass of 1900 kg. Which of the following statements is (are) true? I. The minivan undergoes the larger change in momentum. II. The car undergoes the larger change in velocity. III. Both vehicles have the same magnitude of momentum after 5 seconds. IV. Both vehicles have the same kinetic energy after 5 seconds. A) III and IV. B) I and IV. C) II only. D) II and III. E) III only. 10. A 0.75kg hard rubber ball is dropped from a height of 2.0 m. It hits a concrete floor and rebounds with a speed (just after the collision) that is exactly half the speed it hit with. The ball is in contact with the floor for 0.012 s. What average force does the ball exert on the floor during the collision? A) 587 N upward B) 587 N downward C) 196 N upward D) 196 N downward E) Need more information Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 7 11. Assuming the Earth orbits the sun in a circular orbit, what is the angular speed, ω, for the Earth? A) 4.99×10 -7 radians/s B) 3.15×10 -7 radians/s C) 2.99×10 -7 radians/s D) 4.32×10 -7 radians/s E) 1.99×10 -7 radians/s 12. A bomb initially at rest explodes into three pieces. Two of the pieces have the same mass, and they fly apart with the same speed but in opposite directions. What will the third piece do? A) The third piece will be at rest. B) Need more information C) The third piece will fly parallel to the direction of the other two, with undetermined velocity. D) There is no solution compatible with momentum conservation. E) The third piece will fly perpendicularly to the direction of the other two, with undetermined velocity. Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 8 13. Three packages with back issues of Salami News magazines are being pulled with constant force to the right across a horizontal, frictionless surface, as shown below. As the packages slide a distance d to the right, what is the change in the kinetic energy of box m 2 ? A) (T 2 –T 1 ) d B) (T 2 +T 1 ) d C) (T 3 –T 2 ) d D) T 3 d E) –T 1 d 14. A crate of mass 12.0 kg is pulled 4.00 m up a rough incline at a constant speed. The pulling force is 90.0 N parallel to the incline, which makes an angle of 30 o with the horizontal. How much energy is lost because of friction? A) 11.9 J B) 31.9 J C) 47.8 J D) 595 J E) 125 J 30 o F pull 4.00 m Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 9 15. A racecar is traveling at constant speed around a circular track. What happens to the centripetal acceleration of the car if the speed is doubled? A) The centripetal acceleration is decreased by a factor of one-fourth. B) The centripetal acceleration remains the same. C) The centripetal acceleration increases by a factor of 2. D) The centripetal acceleration increases by a factor of 4. E) The centripetal acceleration is decreased by a factor of one-half. 16. As a 0.2 kg frog leaps at a forward angle, the components of its initial velocity are 2 m/s horizontally and 3 m/s vertically. What is its kinetic energy at the highest point of its trajectory? A) 0.9 J B) 1.3 J C) 0.4 J D) 2.5 J E) 0 J Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 10 17. In the figure, the skier, m = 70 kg, starts with a speed of 10.0 m/s at the top of a hill of height, h, and travels over a second hill that has a radius of curvature, r = 20 m. If air resistance does work on the skier, W Air = −1671 J, between the first hill and the top of the second, what is the height, h, such that the skier just lose contact at the top of the second hill. A) 6.2 m B) 6.3 m C) 10 m D) 7.7 m E) 7.3 m 18. A speeding roller coaster (358 kg) moves from A (3.88 m above the ground) to B (24.2 m above the ground). Two non-conservative forces are present: friction does −2.28×10 4 J of work on the car, and a chain mechanism does +5.38×10 4 J of work to help the car up a long climb. The change in the car's kinetic energy KE f – KE 0 from A to B is close to A) −40300 J. B) 0 J. C) 40300 J. D) −67500 J. E) 67500 J. Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 11 19. The Volkswagon Beetle Turbo S has an engine with a power rating of 180 horsepower (hp), where 1 hp = 746 W. Take the mass of the driver and car to be 1470 kg. Accelerating from a standing start on a level track, what is the fastest speed the car + driver could possibly reach after 6.0 s? (Note: Use 1609 m = 1 mile.) A) 84.3 mi/hr B) 74.1 mi/hr C) 89.2 mi/hr D) 81.1 mi/hr E) 77.5 mi/hr 20. A pumpkin of mass m is hung from a string of length L that is momentarily held horizontally and then released. It collides in a completely inelastic fashion with another pumpkin of mass 3m. To what height h above the collision point will the pair of pumpkins rise? A) L/4 B) L/8 C) L/32 D) L/16 E) L/2 h y=0 y=L Physics 125 Fall 2006 Exam 2 11/02/2006 Form #1 12 Answer Key 1. A 2. C 3. A 4. A 5. E 6. A 7. B 8. B 9. D 10. B 11. E 12. A 13. A 14. E 15. D 16. C 17. E 18. A 19. B 20. D atomasch Microsoft Word - exam2_f06_a.doc