1. © 2005 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. All recipients of this work are expected to abide by these restrictions and to honor the intended pedagogical purposes and the needs of other instructors who rely on these materials. ConcepTest PowerPoints Rotational Motion Parts of Chapters 7, 8,& 9 Physics: Principles with Applications, 6 th edition Giancoli

2. Where is center of mass of a baseball bat located? 1) at the midpoint 2) closer to the thick end 3) closer to the thin end (near handle) 4) it depends on how heavy the bat is ConcepTest 7.18Baseball Bat ConcepTest 7.18 Baseball Bat

3. Two equal-mass particles (A and B) are located at some distance from each other. Particle A is held stationary while B is moved away at speed v. What happens to the center of mass of the two-particle system? 1) it does not move 2) it moves away from A with speed v 3) it moves toward A with speed v 4) it moves away from A with speed 1/2 v 5) it moves toward A with speed 1/2 v ConcepTest 7.19Motion of CM ConcepTest 7.19 Motion of CM

4. ConcepTest 7.20Center of Mass ConcepTest 7.20 Center of Mass (1) X CM (2) 1) higher 2) lower 3) at the same place 4) there is no definable CM in this case The disk shown below in (1) clearly has its center of mass at the center. Suppose the disk is cut in half and the pieces arranged as shown in (2). Where is the center of mass of (2) as compared to (1) ?

5. ConcepTest 8.1aBonnie and Klyde I Bonnie Klyde Bonnie sits on the outer rim of a merry-go-round, and Klyde sits midway between the center and the rim. The merry-go-round makes one complete revolution every two seconds. Klyde’s angular velocity is: 1) same as Bonnie’s 2) twice Bonnie’s 3) half of Bonnie’s 4) 1/4 of Bonnie’s 5) four times Bonnie’s

6. ConcepTest 8.1bBonnie and Klyde II Bonnie Klyde 1) Klyde 2) Bonnie 3) both the same 4) linear velocity is zero for both of them Bonnie sits on the outer rim of a merry- go-round, and Klyde sits midway between the center and the rim. The merry-go-round makes one revolution every two seconds. Who has the larger linear (tangential) velocity?

7. Suppose that the speedometer of a truck is set to read the linear speed of the truck, but uses a device that actually measures the angular speed of the tires. If larger diameter tires are mounted on the truck instead, how will that affect the speedometer reading as compared to the true linear speed of the truck? 1) speedometer reads a higher speed than the true linear speed 2) speedometer reads a lower speed than the true linear speed 3) speedometer still reads the true linear speed ConcepTest 8.2 Truck Speedometer

8. An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle  in the time t, through what angle did it rotate in the time 1/2 t? 1) 1/2  2) 1/4  3) 3/4  4) 2  5) 4  ConcepTest 8.3aAngular Displacement I

9. An object at rest begins to rotate with a constant angular acceleration. If this object has angular velocity  at time t, what was its angular velocity at the time 1/2 t? 1) 1/2  2) 1/4  3) 3/4  4) 2  5) 4  ConcepTest 8.3bAngular Displacement II

10. ConcepTest 8.4Using a Wrench You are using a wrench to loosen a rusty nut. Which arrangement will be the most effective in loosening the nut? 1 3 4 2 5) all are equally effective

11. Two forces produce the same torque. Does it follow that they have the same magnitude? 1) yes 2) no 3) depends ConcepTest 8.5Two Forces

12. ConcepTest 8.6Closing a Door In which of the cases shown below is the torque provided by the applied force about the rotation axis biggest? For all cases the magnitude of the applied force is the same. 1) F 1 2) F 3 3) F 4 4) all of them 5) none of them

13. When a tape is played on a cassette deck, there is a tension in the tape that applies a torque to the supply reel. Assuming the tension remains constant during playback, how does this applied torque vary as the supply reel becomes empty? 1) torque increases 2) torque decreases 3) torque remains constant ConcepTest 8.7Cassette Player

14. ConcepTest 8.8aDumbbell I 1) case (a) 2) case (b) 3) no difference 4) It depends on the rotational inertia of the dumbbell. A force is applied to a dumbbell for a certain period of time, first as in (a) and then as in (b). In which case does the dumbbell acquire the greater center-of- mass speed?

15. 1) case (a) 2) case (b) 3) no difference 4) It depends on the rotational inertia of the dumbbell. A force is applied to a dumbbell for a certain period of time, first as in (a) and then as in (b). In which case does the dumbbell acquire the greater energy? ConcepTest 8.8bDumbbell II

16. ConcepTest 8.9Moment of Inertia a) a) solid aluminum b) hollow gold c) same same mass & radius solid hollow Two spheres have the same radius and equal masses. One is made of solid aluminum, and the other is made from a hollow shell of gold. Which one has the bigger moment of inertia about an axis through its center?

17. ConcepTest 8.10Figure Skater 1) the same 2) larger because she’s rotating faster 3) smaller because her rotational inertia is smaller A figure skater spins with her arms extended. When she pulls in her arms, she reduces her rotational inertia and spins faster so that her angular momentum is conserved. Compared to her initial rotational kinetic energy, her rotational kinetic energy after she pulls in her arms must be

18. ConcepTest 8.11Two Disks ConcepTest 8.11 Two Disks 1) disk 1 2) disk 2 3) not enough info Two different spinning disks have the same angular momentum, but disk 1 has more kinetic energy than disk 2. Which one has the bigger moment of inertia? L L Disk 1 Disk 2

19. ConcepTest 8.12 Spinning Bicycle Wheel You are holding a spinning bicycle wheel while standing on a stationary turntable. If you suddenly flip the wheel over so that it is spinning in the opposite direction, the turntable will 1) remain stationary 2) start to spin in the same direction as before flipping 3) start to spin in the same direction as after flipping

20. ConcepTest 9.1Balancing Rod 1kg 1m A 1 kg ball is hung at the end of a rod 1 m long. If the system balances at a point on the rod 0.25 m from the end holding the mass, what is the mass of the rod? 1) 1/4 kg 2) 1/2 kg 3) 1 kg 4) 2 kg 5) 4 kg

21. ConcepTest 9.2Mobile 1 kg 1 m3 m 1 m2 m ? ? A (static) mobile hangs as shown below. The rods are massless and have lengths as indicated. The mass of the ball at the bottom right is 1 kg. What is the total mass of the mobile? 1) 5 kg 2) 6 kg 3) 7 kg 4) 8 kg 5) 9 kg

22. ConcepTest 9.3aTipping Over I 123 1) all 2) 1 only 3) 2 only 4) 3 only 5) 2 and 3 A box is placed on a ramp in the configurations shown below. Friction prevents it from sliding. The center of mass of the box is indicated by a blue dot in each case. In which case(s) does the box tip over?

23. ConcepTest 9.3bTipping Over II 1) case 1 will tip 2) case 2 will tip 3) both will tip 4) neither will tip Consider the two configurations of books shown below. Which of the following is true? 1/2 1/4 1/2 1/4 12