Name: Exam 4--PHYS 101--Fall 2016 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A bus contains a 2000 kg flywheel (a disk that has a 0.500 m radius) and has a total mass of 10,000 kg. Calculate the angular velocity the flywheel must have to contain enough energy to take the bus from rest to a speed of 20.0 m/s, assuming all of the rotational kinetic energy can be transformed into translational energy. 3. Consider this object. It is a square, flat piece of metal. Each dot shows an axis of rotation; the plate rotates around the axis in the plane of the page. Which of these describe the moments of inertia for the object? a. 45 rad/s b. 130 rad/s c. 14,000 rad/s d. 20 rad/s 2. Two objects have the same angular momentum. Object 1 is spinning twice as fast as object 2. If the energy of object 2 is 10 J, what is the energy of object 1? a. I C >I B >I D >I A b. I C >I B =I D >I A c. I A >I B >I D >I C d. I D >I B >I C >I A e. I A >I B =I D >I C 4. This figure shows a disk with radius equal to 2.0 m; the disk has a mass of 3.0 kg. A mass is attached at the edge of the disk. This mass is 4.0 kg. The system rotates at the pivot point as shown (the x ). What is the moment of inertia for this system? a. 40 J b. 5 J c. 2.5 J d. 20 J e. 10 J a. 28 kg m 2 b. 22 kg m 2 c. 14 kg m 2 d. 24 kg m 2 e. 20 kg m 2 1
5. A bar has a moment of inertia of 8 kg m 2 and is rotating at 2 rev/s in the counter-clockwise direction. It engages with a flywheel, which is rotating in the clockwise direction at 4 rev/s and has a moment of inertia of 16 kg m 2. After they engage, both move at the same speed. What is this new speed? 7. Consider this figure of a rod rotating about the axis labeled C. The mass of the rod is 3.0 kg. What is the net torque? a. 2.0 rev/s, clockwise b. 4.2 rev/s clockwise c. 6.0 rev/s, clockwise d. 3.3 rev/s, counterclockwise e. 1 rev/s, counterclockwise 6. Two 20 kg children are sitting on a merry-go-round that is rotating at 0.10 rad/s. If one child is 1.0 m from the center and the other is 0.5 m from the center, what is their combined angular momentum? a. 40. Nm clockwise b. 30. Nm clockwise c. 22 Nm clockwise d. 20. Nm counterclockwise 8. Consider the bar in the previous problem. After 2 seconds of the net torque acting on the rod, what is the rod s angular velocity? a. 0.25 kg m 2 /s b. 0.5 kg m 2 /s c. 0.75 kg m 2 /s d. 1.0 kg m 2 /s e. 2.5 kg m 2 /s a. 60 rad/s b. 15 rad/s c. 1.3 rad/s d. 12 rad/s 2
9. When will an object continue spinning at the same angular velocity? a. when the net torque is zero b. when the net torque is non-zero c. when the angular acceleration is positive d. when the angular acceleration is negative e. when the net force on the object is zero 10. A rectangular boat is 2.0 m by 1.0 m by 2.0 m. What total mass (including the mass of the boat) is the boat able to keep afloat? a. 40 kg b. 4000 kg c. 25 kg d. 500 kg e. 50,000 kg 11. A boat carrying a large chunk of steel is floating on a lake. The chunk is then thrown overboard and sinks. The water level in the lake drops. Why? a. the steel displaces more water when in the boat than when submerged b. the steel has a lower apparent mass when it is submerged c. the boat weighs less when it doesn t have the steel d. the steel experiences a greater buoyant force when it is completely submerged 13. The flow velocity in a 2.0-cm-diameter tube is 0.010 m/s. If a tube restriction narrows the tube down to 1.0 cm in diameter, the flow in this region is a. 0.010 m/s b. 0.020 m/s c. 0.030 m/s d. 0.040 m/s 14. A straightforward method of finding the density of an object is to measure its mass and then measure its volume by submerging it in a graduated cylinder. A material displaces 93.3 ml of water. It has a mass of 1800 g. What is the substance? a. Silver b. Gold c. Platinum d. Aluminum 15. Pascal s principle says: a. energy is conserved in a flowing ideal fluid b. a small input force always causes a large output force c. matter must be conserved in a flowing ideal fluid d. a change in pressure at one point in an incompressible fluid is felt at every other point in the fluid e. the buoyant force equals the weight of the displaced fluid 12. Water flows through a pipe. The pressure is 2000 Pa, and the water flows at 1.0 m/s. The pressure in the next section of pipe drops to 1000 Pa. What has happened to the pipe? a. the pipe has gotten narrower b. the pipe has gotten bigger c. the pipe has remained the same size d. it is not possible to know what has happened to the pipe 3
16. This figure shows the essential parts of a hydraulic brake system. The area of the piston in the master cylinder is 2.4 cm 2, and that of the piston in the brake cylinder is 9.6 cm 2. If the driver applies a force to the master cylinder, via his brake pedal, of 16 N. How much force is applied to the brake pedal? 18. Estimate the pressure a person, standing on one foot, exerts on that foot. a. 20,000 N/m 2 b. 2,000 N/m 2 c. 200 N/m 2 d. 20 N/m 2 19. For water which state is the most dense? a. solid b. liquid c. gas d. all have the same density a. 4 N b. 8 N c. 16 N d. 32 N e. 64 N 17. This manometer is measuring the pressure, P. The known pressure, P 0, is 1.0 atm. The height of the column, h, is 0.10 m. The liquid in the manometer is mercury (Hg). What is the pressure P? 20. A 10-meter rope has a diameter of 0.02 m. When you pull on it with a force of 1000 N, the rope stretches 1.0 cm. What is the Young s modulus for the rope? a. 8.0x10 8 pascals b. 3.2x10 9 pascals c. 9.0x10 9 pascals d. 4.5x10 9 pascals a. 0.86 atm b. 1.1 atm c. 32,000 atm d. 0.32 atm e. 1.0 atm 4
21. A rigid container has a volume of 0.5 m 3 and holds 30 moles of gas. If the gas is at room temperature (20ºC), what is the pressure of the gas? (Beware of units!) 25. The celsius scale is based upon which of these quantities: I. Absolute Zero II. Freezing point of Water III. Triple point of water IV. Boiling point of water a. II & III b. II & IV c. I & IV d. I & III 26. Two objects are in thermal equilibrium. Which of these statements are necessarily true? a. 30 Pa b. 1000 Pa c. 1.5 atm d. 0.01 atm 22. Which has a greater number of atoms, a mole of nitrogen gas or a mole of oxygen gas? (the molar mass of nitrogen is 14.007; the molar mass of oxygen is 15.999) a. nitrogen b. oxygen c. both the same d. not enough information I. The objects have the same mass. II. The objects have the same specific heat. III. The objects have the same temperature. IV. The objects have the same density. a. II only b. I & IV c. I & III d. II & III e. III only 27. Dr. Young thinks I m awesome!! a. True b. False 23. You have a steel rod that is stuck in a concrete block. Which of these is the best solution to remove the rod? a. cool the steel rod and the concrete block b. heat the steel rod c. cool the concrete block d. heat the steel rod and the concrete block 24. 20 C is equivalent to what temperature in degrees fahrenheit? a. 212 F b. 32 F c. 70 F d. 100 F 5
ID: A Exam 4--PHYS 101--Fall 2016 Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 1 REF: F16-OS 2. ANS: D PTS: 1 REF: F16 3. ANS: E PTS: 1 REF: F16 4. ANS: B PTS: 1 REF: F16 5. ANS: A PTS: 1 REF: F16 6. ANS: E PTS: 1 REF: F16-OS 7. ANS: B PTS: 1 REF: F16 8. ANS: B PTS: 1 REF: F16 9. ANS: A PTS: 1 REF: F16 10. ANS: B PTS: 1 REF: F16 11. ANS: A PTS: 1 REF: F16 12. ANS: A PTS: 1 REF: F16 13. ANS: D PTS: 1 REF: F16 14. ANS: B PTS: 1 REF: F16-OS 15. ANS: D PTS: 1 REF: F16 16. ANS: E PTS: 1 REF: F16 17. ANS: B PTS: 1 REF: F16 18. ANS: A PTS: 1 REF: F16 19. ANS: B PTS: 1 REF: F16 20. ANS: B PTS: 1 REF: F16 21. ANS: C PTS: 1 REF: F16 22. ANS: C PTS: 1 REF: F16 23. ANS: D PTS: 1 REF: F16 24. ANS: C PTS: 1 REF: F16 25. ANS: B PTS: 1 REF: F16 26. ANS: E PTS: 1 REF: F16 27. ANS: A PTS: 1 1