Physics 23 - Fall 2006a Answer Sheet Printed Name: Recitation Instructor EM Mini-Test Rec Sec & Final Exam Student ID Gently remove this page from your exam when you begin. Write clearly in the space provided on this Answer Sheet the letter which you believe to be the best answer to each question on the Mini-Test and on the Final Exam, found on the following pages. Neither calculators nor notes can be used during the test. Each question on the End-Material Mini Test is worth 10 points, and on the Final Exam 6 points. Relax, Read carefully, Think S and then read it again!!! If you become bogged down on a problem, go to the next one and return later to the hard one. Think before plunging into math manipulations. Basic principles may give you an easy answer. Never leave a multiple-choice question blank. Guess at the end if you must. EM Mini-Test Score = Mini-Test Responses (10 pts each) Final-Exam Score = Final-Exam Responses (6 pts each) em - 1) 1) 16) em - 2) 2) 17) em - 3) 3) 18) em - 4) 4) 19) em - 5) 5) 20) em - 6) 6) 21) 7) 22) 8) 23) 9) 24) 10) 25) 11) 26) 12) 27) 13) 28) 14) 29) 15) 30)
Physics 23!Fall 2006a END-MATERIAL MINI-TEST em-1. A sphere of radius R placed in water and floats with the top of the sphere a distance R above the surface of the water. If the density of water is ρ, what is the mass of the sphere? A) ¼ ρr B) b πρr 3 C) 4 /3 πρr 3 D) b πρgr 3 em-2. A race car in the Indianapolis 500 is traveling at ¼V, where V is the speed of sound. An excited spectator blows an airhorn with frequency f as the racer passes by. Assuming the racer can hear the airhorn, what frequency does the racer hear after passing by the spectator? (Assume the spectator is in the direct path of the car.) A) ¾ f B) ¼ f C) 5 /4 f D) ½ f em-3. Two loudspeakers (A and B) are placed 12 m apart. They are driven by the same oscillator so they emit in phase and generate waves of wavelength 4 m. You put a detector at point P that is 8 m along the perpendicular bisector between the speakers. If each wave independently has amplitude A at point P what is the amplitude of the resultant wave at P? A) zero B) A C) 2A D) A/2 em-4. Two conducting cubes, A and B, are each placed between heat reservoirs at temperatures T hot and T cold. Cube A has sides of length L, while Cube B has sides of length ½L. The thermal conductivity of Cube B is half that of Cube A. Their side walls are insulated so there is no heat loss through them, so heat energy flow only between the reservoirs. What is the rate of thermal energy transfer through Cube A divided by rate through Cube B? A) ½ B) 1 C) 2 D) 4 An ideal diatomic gas is taken through the cycle A6B6C6A shown in the P-V diagram at the below. Use this diagram to answer the next two questions. em-5. Which process step is isobaric? A) A6B B) B6C C) C6A D) none of the above. em-6. How much heat is absorbed in process step B6C? A) 15(P o V o ) B) 3(P o V o ) C) 20(P o V o ) D) 20(P o V o ) EM (F06a)
Physics 23 - Fall 2006a FINAL EXAM Assume that g = 10 m/s 2 and that air-resistance is negligible unless otherwise stated! 1. An object is thrown upward at some initial angle (less than 90 o ) relative to the vertical y-axis. When the object reaches the maximum height we know that A) v y =0, a=g B) v=0, a=g C) v x =0, a x = 0 D) v y =0, a= g 2. A block is sliding in the positive x-direction along a horizontal rough surface. The direction of the force of friction exerted on the block by the surface A) in the negative x-direction B) same as the direction of the normal force C) in the positive x-direction D) depends on the acceleration direction of block. 3. A 6-kg block is attached to a 2-kg block by a light cable. They are pulled along a frictionless surface by a horizontal force of magnitude 80 N applied to the 6-kg block, as shown in the figure. What is the string s tension? A) 40 N B) 50 N C) 20 N D) 80 N 4. You throw a ball with initial speed V o at angle θ with the vertical. When it reaches a height H on the way up, the vertical component of its velocity is: A) (2gH) ½ B) V 0 cosθ C) (cos 2 2 θ V o +2gH) ½ D) (cos 2 2 θ V o 2gH) ½ 5. An object of mass m is moving on a frictionless, horizontal table in a circle with constant radius R. It moves with constant speed v 0. It is held in its path by a massless cord that is connected to a dangling block of mass M through a hole in the center. If the speed of the object is increased to 2 v 0 and the radius R is kept constant, the new mass of the dangling block must be A) 4 M B) 2 M C) ½ M D) M 6. A block of mass 15 kg is placed in the flat area in the back of a truck. The truck accelerates at 3 m/s 2 on a horizontal road. To make sure that the block does not slide relative to the truck, a worker pushes straight down on the crate with a 50-N force. The coefficient of static friction between the crate and truck is 0.25. Assuming g = 10 m/s 2, the magnitude of the horizontal component of the net force acting on the crate is: A) 40 N B) 45 N C) 50 N D) 30 N FE-1 (F06a)
7. Which of the following guarantees that vectors AP and BP are perpendicular? A) AP BP=0 B) AP BP=0 C) AP+BP=0 D) A x =B x =0 8. An archer, standing in a very large and flat level field, shoots a light-weight arrow into the air at an angle of less than 90 o from the horizontal. Next she shoots an arrow of a larger weight under exactly the same conditions (including angle and initial velocity). Which of the following is true? A. The light-weight arrow travels farther horizontally to impact. B) The higher weight arrow travels farther horizontally to impact. C) Both arrows travel the same distance horizontally to impact. D) The light-weight arrow stays in the air longer than the more massive arrow. 9. A 10-kg mass is initially moving only vertically upward at 3 m/s. It then experiences a constant net force of 10 N horizontally for 4 seconds. What is the speed of the mass after 4 seconds? A) 7 m/s B) 5 m/s C) 4 m/s D) 1 m/s 10. A stone is thrown horizontally with speed V from the top of a cliff of height H, as shown in the diagram. How much time will elapse before the stone hits the ground? A) H/V B) [!2H/g] ½ C) [½g/H ] ½ D) [2H/g] ½ 11. A stationary shell explodes into two pieces with unequal masses m 1 <m 2. One can conclude the following about their speeds A) v 1 >v 2 B) v 1 <v 2 C) v 1 =v 2 D) The sum of the speeds = 0 12. Two satellites are placed on different circular orbits around the Earth. Choose the statement that accurately describes the situation A) the satellite on the lower orbit travels faster B) the satellite on the higher orbit travels faster C) both satellites move with the same speed D) not enough information is given to compare the speeds of the satellites 13. A block of mass M is released at height H and slides down a frictionless incline as shown in the figure. The block comes to rest after it has traveled an unknown distance L on the horizontal surface with coefficient of kinetic friction μ. What does L equal? A) Hμ/Mg B) H sinθ/μ C) H/[μ sinθ] D) H/μ FE-2 (F06a)
14. Which of the following forces is a conservative force? A) spring force B) air resistance C) kinetic friction D) static friction 15. Select the statement which best characterizes the force of friction: A) force of static friction is always greater than the force of kinetic friction B) force of static friction is always smaller than the force of kinetic friction C) depending on the circumstances, force of static friction can be smaller or greater than the force of kinetic friction D) both static and kinetic friction forces are the same 16. On returning a tennis ball of mass m, a tennis player s racket applies a constant horizontal force of magnitude F. Assuming that initially the ball moves with the speed v 0 in the direction opposite to that of the force, what should the duration of the impact be in order to reverse the ball s velocity? A) mv 0 /(2F) B) 2F/(mv 0 ) C) 2mv 0 /F D) F/(2mv 0 ) 17. Two planets with identical radii R and masses M have a center to center distance of 4R. A projectile of mass m is shot from the surface of Planet A with initial speed V 0. Provided that it is shot from the closest point on Planet A and lands on the closest point of Planet B, as shown, what is its speed when it reaches the surface of planet B? A) [V 0 2 2GM/(3R)] ½ B) [V 0 2 +2GM/(3R)] ½ C) V 0 2GM/(3R) D) V 0 18. In a collision between two objects, which of the following is true? A) total mechanical energy and total momentum are conserved B) total mechanical energy is conserved, additional information is needed to determine whether the total momentum is conserved C) total momentum is conserved, additional information is needed to determine whether the total mechanical energy is conserved D) additional information is needed to determine whether the total mechanical energy and/or total momentum is conserved 19. If you have one apple and someone gives you another apple, how many apples do you have? (We bet you were concerned we wouldn t give you a question like this.) A) 1 B) 2 C) 3 D) 4 FE-3 (F06a)
20. A worker is dragging a crate of mass M by applying a force F at an angle θ as shown. The coefficient of kinetic friction between the crate and the floor is μ. What is the work done by the worker to move the crate a distance L? A) FL B) FLcosθ C) FLcosθ MgμL D) (Mg Fsinθ)μL 21. The moment of inertia is largest if a solid uniform rectangle rotates about a A) vertical (up-down) line passing through its left end B) horizontal (left-right) line passing through its top end C) vertical (up-down) line passing through point P D) horizontal (left-right) line passing through point C 22. You have three identical particles, A,B,C. Particles A and B are attached to a disk that is rotating about its center with angular speed ω. C is traveling in a straight line with linear speed v = ½ ωr. Which of the following is a correct statement about their angular momenta? A) L A = L B B) L B = L C C) L A = L C D) All are different 23. Four cylinders having the same mass and outer radius but different mass distributions as shown at the right. If all are rolling without slipping along a flat horizontal surface and all have the same kinetic energy, which has the largest linear speed? A) a B) b C) c D) d 24. A block of weight W is suspended from the end of a horizontal uniform beam of length L and weight W. One end of the beam is glued to the wall, the other is attached to the ceiling by a light rope as shown in the figure. What is the tension in the light rope from the ceiling to the beam? A) 2W/cos1 B) 3 /2 W/sin1 C) 2W/sin1 D) ½W/cos1 25. Which statement is correct about the figure at the right? A) the rod will rotate in a clockwise direction about point P B) the rod will rotate in a counterclockwise direction about point P C) the rod will move horizontally or vertically D) the rod is in static equilibrium FE-4 (F06a)
26. A mass attached to a massless spring is undergoing simple harmonic motion with amplitude R. At what position is the potential energy twice the magnitude of the kinetic energy? A) [b] ½ R B) [a] ½ R C) ½ R D) 3 /2 R 27. A chain is wrapped around two solid cylindrical sprockets T and B, each of mass M, that are free to rotate on frictionless axles as shown. The top sprocket T has twice the diameter as the bottom sprocket B. You attach a block of weight magnitude W to one end and pull on the other end with force of magnitude P such that the weight moves upwards with constant speed. Which statement is true? A) P > W B) α t > α b C) ω t = ω b D) Σ τ z (for top sprocket) = Σ τ z (for bottom sprocket) 28. A bucket of mass M hangs from a rope that passes over the top of a uniform solid pulley of mass 2M and radius 2R. The two ends of the rope makes angle θ with each other as shown. The rope does NOT slip on the pulley. If you pull the rope with force magnitude P = 2Mg, the bucket accelerates upwards. What is the magnitude of the pulley s angular acceleration? A) ½ g B) ½ g[2cos θ - 1]/R C) 2g D) g[2cos θ - 1]/R 29. A bucket of mass M is hanging motionless from a rope that passes over the top of a uniform solid pulley of mass M and radius R. If you pull on the rope, the bucket moves upwards. After it has moved upwards a distance h, it has speed v. What is the magnitude of the work done by pulling on the rope? Note: The rope does NOT slip on the pulley. A) ½ Mv 2 + Mgh B) Mv 2 + Mgh C) ¾ Mv 2 + Mgh D) ¼ Mv 2 + Mgh 30. A particle of mass M is traveling in a straight line with constant velocity. The relationships between the magnitudes of its angular momentum with respect to point P at positions 1, 2, and 3 is: A) L 1 > L 3 > L 2 B) L 1 = L 2 = L 3 C) L 1 < L 3 < L 2 D) L 1 > L 2 > L 3 The teaching staff of Physics 23 all wish you a happy and wondrous holiday season! FE-5 (F06a)