PhysicsBowl 2007 PDF Past Paper

ATTENTION: All Division I students, START HERE. All Division II students, skip the first ten questions, begin on question 11. 1. A standard centimeter ruler is shown. Which recorded value is the most correct for the location of the shaded objec...

ATTENTION: All Division I students, START HERE. All Division II students, skip the first ten questions, begin on question 11. 1. A standard centimeter ruler is shown. Which recorded value is the most correct for the location of the shaded object’s right end? (a) 10 cm (b) 10. cm (c) 10.0 cm (d) 10.00 cm (e) 10. 0 cm 2. How thick is the average page of a physics textbook in micrometers? (a) 0.1 (b) 1 (c) 10 (d) 100 (e) 1000 3. Two automobiles are 150 kilometers apart and traveling toward each other. One automobile is moving at 60 km/h and the other is moving at 40 km/h. In how many hours will they meet? (a) 1.5 (b) 1.75 (c) 2.0 (d) 2.5 (e) 3.0 4. A particle moves on the x-axis. When the particle’s acceleration is positive and increasing (a) its velocity must be positive. (b) its velocity must be negative. (c) it must be slowing down. (d) it must be speeding up. (e) none of the above must be true. 5. The position-time, y vs. t, graph for the motion of an object is shown. What would be a reasonable equation for the acceleration a that would account for this motion? (a) a=0 (b) a = positive constant (c) a = negative constant (d) a = positive constant times t (e) a = negative constant times t Division I only 2 Division I only 6. A 500-kg car is moving at 28 m/s. The driver sees a barrier ahead. If the car takes 95 meters to come to rest, what is the magnitude of the minimum average net force necessary to stop? (a) 47.5 N (b) 1400 N (c) 2060 N (d) 19600 N (e) 133000 N 7. A mass connected to a string swings back and forth as a pendulum with snapshots of the motion seen in the figure. Ignore the friction in the system. Which of the following statements about the pendulum-Earth A system is correct? E (a) The total mechanical energy in the system is constant. B D (b) The total mechanical energy in the system is maximum at B. C (c) The potential energies at A and C are equal. (d) The kinetic energies at C and D are equal. (e) The kinetic energy at E equals the kinetic energy at C. 8. What does one obtain by dividing the distance of 12 Mm by the time of 4 Ts? (a) 3 nm (b) 3 µ m (c) 3 mm (d) 3 km (e) 3 Gm s s s s s 9. A block rests on an incline that makes the angle φ with the horizontal. The block remains at rest as φ is slowly increased. The magnitudes of the normal force and the static frictional force of the incline on the block (a) both increase. (b) both decrease. (c) both remain the same. (d) increase and decrease, respectively. (e) decrease and increase, respectively. 10. Contact forces are examples of which of the fundamental forces? (a) Strong (b) Electromagnetic (c) Weak (d) Gravitational (e) None of these ATTENTION: All Division I students, turn page and continue through question 40. Division I only 3 Division I only ATTENTION: All Division I students, continue through question 40. All Division II students, START HERE. Numbers 1-10 on your answer sheet should remain blank. Your first answer should be number 11. 11. A cart is initially moving at 0.5 m/s along a track. The cart comes to rest after traveling 1 m. The experiment is repeated on the same track, but now the cart is initially moving at 1 m/s. How far does the cart travel before coming to rest? (a) 1 m (b) 2 m (c) 3 m (d) 4 m (e) 8 m 12. The definition of average velocity is (a) the average acceleration multiplied by the time. (b) distance traveled divided by the time. (c) 1 (v f + v0 ). 2 (d) radius multiplied by angular velocity. (e) displacement divided by the time. 13. A student weighing 500 N stands on a bathroom scale in the school’s elevator. When the scale reads 520 N, the elevator must be (a) accelerating upward. (b) accelerating downward. (c) moving upward at a constant speed. (d) moving downward at a constant speed. (e) at rest. 14. An object moves to the East across a frictionless surface with constant speed. A person then applies a constant force to the North on the object. What is the resulting path that the object takes? (a) A straight line path partly Eastward, partly Northward (b) A straight line path totally to the North (c) A parabolic path opening toward the North (d) A parabolic path opening toward the East (e) An exponential path opening upward toward the North Both Divisions I and II 4 Both Division I and II Two identical mass objects are launched with the same speed from the same starting location. Object 1 is launched at an angle of 300 above the horizontal while Object 2 is launched at an angle of 60 0 above the horizontal. Ignore air resistance and consider the flight of each object from launch until it returns to the same launch height above the ground. Questions 15 and 16 refer to this situation. 15. Which object returns to the starting height with the greatest speed? (a) Object 1 since it keeps a lower trajectory. (b) Object 2 since it is in the air for a longer time. (c) Object 2 since there is more work done on the object during flight (d) The speeds are the same. (e) It cannot be determined without more information. 16. Which object experiences the greatest change in the linear momentum? (a) Object 1 since it has a higher final speed. (b) Object 2 since it has a higher final speed. (c) Object 2 since it is in the air for a longer time. (d) The change in momentum is the same for each. (e) It cannot be determined without more information. 17. A toy car moves along the x-axis according to the velocity versus time curve shown to the right. When does the car have zero acceleration? (a) at 2 and 4 seconds (b) at approximately 3.0 seconds (c) at approximately 3.3 and 5.1 seconds (d) the acceleration is always zero (e) at no time 18. In which one of the following situations is the net force constantly zero on the object? (a) A mass attached to a string and swinging like a pendulum. (b) A stone falling freely in a gravitational field. (c) An astronaut floating in the International Space Station. (d) A snowboarder riding down a steep hill. (e) A skydiver who has reached terminal velocity. Both Divisions I and II 5 Both Division I and II 19. What net force is necessary to keep a 1.0 kg puck moving in a circle of radius 0.5 m on a horizontal frictionless surface with a speed of 2.0 m/s? (a) 0 N (b) 2.0 N (c) 4.0 N (d) 8.0 N (e) 16 N 20. A large wedge rests on a horizontal frictionless surface, as shown. A block starts from rest and slides down the inclined surface of the wedge, which is rough. During the motion of the block, the center of mass of the block and wedge system (a) does not move. (b) moves vertically with increasing speed. (c) moves horizontally with constant speed. (d) moves horizontally with increasing speed. (e) moves both horizontally and vertically. 21. A box slides to the right across a horizontal floor. A person called Ted exerts a force T to the right on the box. A person called Mario exerts a force M to the left, which is half as large as the force T. Given that there is friction f and the box accelerates to the right, rank the sizes of these three forces exerted on the box. (a) f < M