ame: Exam 3--PHYS 101--F11--Chapters 7, 8, & 9 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A 1500 kg truck must travel a maximum of 22 m/s around a curve that has a radius of 52 m. What is the coefficient of static friction between the truck s tires and the road? a. 106 c. 1.2 b. 0.45 d. 0.95 2. When a car travels around a curve, what force provides the centripetal force? a. the frictional force between the tires and c. the weight of the car road b. the force provided by the engine d. the normal force of the road 3. A little boy pushes his sister around on a merry-go-round. It begins at rest, and, after 12 seconds, is traveling at 3.6 revolutions per second. How many revolutions does the merry-go-round complete in these 12 seconds? a. 40 rev c. 11 rev b. 3.6 rev d. 22 rev 1
4. A sample of blood is placed in a centrifuge of radius 0.15 m. The mass of a red blood cell is 3.0 10-16 kg, and the magnitude of the force acting on it as it settles out of the plasma is 4.0 10-11 N. At how many radians per second should the centrifuge be operated? a. 1500 rad/s c. 20000 rad/s b. 940 rad/s d. 1.8 10-27 rad/s 5. Kaisa sits on the outer rim of a merry-go-round, and Chad sits midway between the rim and center. The merry-go-round makes 1 revolution every 2 seconds. Chad s angular velocity is... a. four times Kaisa s d. one-quarter of Kaisa s b. one-half of Kaisa s e. same as Kaisa s c. twice Kaisa s 6. How many revolutions is 600 degrees? a. 96 rev c. 1.7 rev b. 2.4 rev d. 3800 rev 7. An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle θ in the time t, through what angle did it rotate in the time 2t? a. 1 4 θ d. 1 2 θ b. 2θ e. c. 4θ 3 4 θ 2
8. What is the net torque acting on this bar about the point C? a. 67 Nm clockwise c. 19 Nm counterclockwise b. 59 Nm counterclockwise d. 12 Nm clockwise 9. A merry-go-round with a mass of 1000 kg has a radius of 2.0 m. It is started from rest by a constant horizontal force of 50.0 N applied tangentially to the merry-go-round. What is its angular velocity after 2.00 s. (Assume it is a solid cylinder.) a. 0.05 rad/s c. 100 rad/s b. 0.2 rad/s d. 0.1 rad/s 3
10. A solid metal sphere whose mass is 12.5 kg has a radius of 1.00 m. It is spinning at a rate of 2.00 rad/s. What is the rotational kinetic energy of the sphere? a. 25.0 J c. 18.9 J b. 10.0 J d. 12.5 J 11. The following figure shows a configuration of particles arranged on an equilateral triangle, whose sides are all 4.0 m. The rotation axis is the dashed line in this figure. What is the moment of inertia for this configuration of charges? a. 64.0 kg m 2 c. 16.0 kg m 2 b. 112 kg m 2 d. 8.00 kg m 2 4
12. Buckets are spinning horizontally on frictionless bearings. Suddenly, it starts raining. Which of these statements is true: a. the buckets will spin at the same angular speed because there is no torque acting on this b. the buckets moment of inertia will increase, causing the buckets angular momentum to increase c. the buckets angular speed will decrease because their moment of inertia is increasing d. None of these are true 13. A merry-go-round has a mass of 100 kg and a radius of 1m. It is spinning at 2 rev/s. A kid with a mass of 50 kg jumps onto the outer rim of the merry-go-round. What is the angular velocity of the merry-go-round after the kid jumps aboard? a. 2 rev/s c. 4 rev/s b. 0.5 rev/s d. 1 rev/s 14. Which of these are the basic SI units for torque? a. kg m s 2 c. kg m s b. m d. kg m2 s 2 15. You want to see-saw with your (much smaller) 3-year old nephew. He sits on the seat of the seesaw. Where should you sit to make this easier? a. on the same side as your nephew c. on the seat. b. at the pivot point d. closer to the pivot point 5
16. Two spheres have the same mass. One sphere is made of aluminum, while the other sphere is made of gold. Both are solid. Because gold is more dense, the radius of the gold sphere is smaller than the aluminum sphere. Which has the larger moment of inertia? a. aluminum sphere c. both the same b. gold sphere d. not enough information 17. This figure shows a barometer, which is filled with mercury. The height of the column of mercury is h=1200 mm. In units of atmospheres, what is the pressure P? a. 1.0 atm c. 1.6 atm b. 0.16 atm d. 92,000 atm 18. Bernoulli s equation is based on which of these laws: a. conservation of charge c. conservation of matter b. conservation of energy d. conservation of momentum 6
19. Water flows through a pipe at 3.0 m/s with a cross-sectional area of 0.5 m 2. The pipe grows wider to 1.0 m 2. What is the speed of the water in the larger pipe? a. 6.0 m/s c. 1.0 m/s b. 1.5 m/s d. 3.0 m/s 20. Consider this hydraulic lift. The area of the left side (A 1 ) is 0.01 m 2, and the area of the right side (A 2 ) is 1.2 m 2. What force (F 1 ) is required to lift a car with a mass of 1000 kg? a. 12 N c. 82 N b. 8.3 N d. 9800 N 21. Consider this section of pipe that narrows as it goes from left to right. An ideal fluid flows through this pipe. Where is the pressure the highest? a. (a) c. (c) b. (b) 7
22. The presence of dark matter was inferred by Vera Rubin by observing a. the mass of muons c. the spin of electrons b. the rotation rates of galaxies d. gamma rays from black holes 23. An aluminum block has a mass of 1200 kg. What is its volume? a. 0.023 m 3 c. 2.3 m 3 b. 0.44 m 3 d. 3.3 10 6 m 3 24. Consider this manometer. Which statement best describes the relationship between P and P 0? a. P>P 0 c. P<P 0 b. P=P 0 d. it depends on the density of the material in the manometer 25. The answer to this question is B. a. A c. C b. B d. D 8
ID: A Exam 3--PHYS 101--F11--Chapters 7, 8, & 9 Answer Section MULTIPLE CHOICE 1. ANS: D PTS: 1 2. ANS: A PTS: 1 3. ANS: D PTS: 1 4. ANS: B PTS: 1 5. ANS: E PTS: 1 6. ANS: C PTS: 1 7. ANS: C PTS: 1 8. ANS: C PTS: 1 9. ANS: D PTS: 1 10. ANS: B PTS: 1 11. ANS: C PTS: 1 12. ANS: C PTS: 1 13. ANS: D PTS: 1 14. ANS: D PTS: 1 15. ANS: D PTS: 1 16. ANS: A PTS: 1 17. ANS: C PTS: 1 18. ANS: B PTS: 1 19. ANS: B PTS: 1 20. ANS: C PTS: 1 21. ANS: A PTS: 1 22. ANS: B PTS: 1 23. ANS: B PTS: 1 24. ANS: C PTS: 1 25. ANS: B PTS: 1 1