Quick Check Questions Chapter 7 Rotational Motion 2015

Quick. Check Questions Chapter 7 Rotational Motion © 2015 Pearson Education, Inc.

Quick. Check 7. 1 A ball rolls around a circular track with an angular velocity of 4 rad/s. What is the period of the motion? A. s B. 1 s C. 2 s D. s E. s © 2015 Pearson Education, Inc. Slide 7 -2

Quick. Check 7. 1 A ball rolls around a circular track with an angular velocity of 4 rad/s. What is the period of the motion? A. s B. 1 s C. 2 s D. s E. s © 2015 Pearson Education, Inc. Slide 7 -3

Quick. Check 7. 2 Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s angular velocity is ______ that of Rasheed. A. B. C. D. E. Half The same as Twice Four times We can’t say without knowing their radii. © 2015 Pearson Education, Inc. Slide 7 -4

Quick. Check 7. 2 Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s angular velocity is ______ that of Rasheed. A. B. C. D. E. Half The same as Twice Four times We can’t say without knowing their radii. © 2015 Pearson Education, Inc. Slide 7 -5

Quick. Check 7. 3 Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s speed is ______ that of Rasheed. A. B. C. D. E. Half The same as Twice Four times We can’t say without knowing their radii. © 2015 Pearson Education, Inc. Slide 7 -6

Quick. Check 7. 3 Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s speed is ______ that of Rasheed. A. B. C. D. E. Half The same as Twice v = ωr Four times We can’t say without knowing their radii. © 2015 Pearson Education, Inc. Slide 7 -7

Quick. Check 7. 4 Two coins rotate on a turntable. Coin B is twice as far from the axis as coin A. A. The angular velocity of A is twice that of B B. The angular velocity of A equals that of B C. The angular velocity of A is half that of B © 2015 Pearson Education, Inc. Slide 7 -8

Quick. Check 7. 4 Two coins rotate on a turntable. Coin B is twice as far from the axis as coin A. A. The angular velocity of A is twice that of B B. The angular velocity of A equals that of B C. The angular velocity of A is half that of B © 2015 Pearson Education, Inc. Slide 7 -9

Quick. Check 7. 5 The fan blade is slowing down. What are the signs of ω and ? A. B. C. D. E. ω is positive and is positive. ω is positive and is negative. ω is negative and is positive. ω is negative and is negative. ω is positive and is zero. © 2015 Pearson Education, Inc. Slide 7 -10

Quick. Check 7. 5 The fan blade is slowing down. What are the signs of ω and ? A. B. C. D. E. ω is positive and is positive. ω is positive and is negative. ω is negative and is positive. ω is negative and is negative. ω is positive and is zero. “Slowing down” means that and have opposite signs, not that is negative. © 2015 Pearson Education, Inc. Slide 7 -11

Quick. Check 7. 6 The fan blade is speeding up. What are the signs of and ? A. B. C. D. is positive and is negative and is positive. is negative and is negative. © 2015 Pearson Education, Inc. Slide 7 -12

Quick. Check 7. 6 The fan blade is speeding up. What are the signs of and ? A. B. C. D. is positive and is negative and is positive. is negative and is negative. © 2015 Pearson Education, Inc. Slide 7 -13

Quick. Check 7. 7 This is the angular velocity graph of a wheel. How many revolutions does the wheel make in the first 4 s? A. B. C. D. E. 1 2 4 6 8 © 2015 Pearson Education, Inc. Slide 7 -14

Quick. Check 7. 7 This is the angular velocity graph of a wheel. How many revolutions does the wheel make in the first 4 s? A. B. C. D. E. 1 2 4 6 8 = area under the angular velocity curve © 2015 Pearson Education, Inc. Slide 7 -15

Quick. Check 7. 8 Starting from rest, a wheel with constant angular acceleration spins up to 25 rpm in a time t. What will its angular velocity be after time 2 t? A. B. C. D. E. 25 rpm 50 rpm 75 rpm 100 rpm 200 rpm © 2015 Pearson Education, Inc. Slide 7 -16

Quick. Check 7. 8 Starting from rest, a wheel with constant angular acceleration spins up to 25 rpm in a time t. What will its angular velocity be after time 2 t? A. B. C. D. E. 25 rpm 50 rpm 75 rpm 100 rpm 200 rpm © 2015 Pearson Education, Inc. Slide 7 -17

Quick. Check 7. 9 Starting from rest, a wheel with constant angular acceleration turns through an angle of 25 rad in a time t. Through what angle will it have turned after time 2 t? A. B. C. D. E. 25 rad 50 rad 75 rad 100 rad 200 rad © 2015 Pearson Education, Inc. Slide 7 -18

Quick. Check 7. 9 Starting from rest, a wheel with constant angular acceleration turns through an angle of 25 rad in a time t. Through what angle will it have turned after time 2 t? A. B. C. D. E. 25 rad 50 rad 75 rad 100 rad 200 rad © 2015 Pearson Education, Inc. Slide 7 -19

Quick. Check 7. 10 The four forces shown have the same strength. Which force would be most effective in opening the door? A. B. C. D. E. Force F 1 Force F 2 Force F 3 Force F 4 Either F 1 or F 3 © 2015 Pearson Education, Inc. Slide 7 -20

Quick. Check 7. 10 The four forces shown have the same strength. Which force would be most effective in opening the door? A. B. C. D. E. Force F 1 Force F 2 Force F 3 Force F 4 Either F 1 or F 3 © 2015 Pearson Education, Inc. Your intuition likely led you to choose F 1. The reason is that F 1 exerts the largest torque about the hinge. Slide 7 -21

Quick. Check 7. 11 Which third force on the wheel, applied at point P, will make the net torque zero? © 2015 Pearson Education, Inc. Slide 7 -22

Quick. Check 7. 11 Which third force on the wheel, applied at point P, will make the net torque zero? A. © 2015 Pearson Education, Inc. Slide 7 -23

Quick. Check 7. 12 Which point could be the center of gravity of this L-shaped piece? D. A. B. C. © 2015 Pearson Education, Inc. Slide 7 -24

Quick. Check 7. 12 Which point could be the center of gravity of this L-shaped piece? D. A. B. C. © 2015 Pearson Education, Inc. Slide 7 -25