# Rotation - Chapter No 9

Right Answers have been shown below in red color.

1. A radian is about:

A. 25◦B. 37◦C. 45◦D. 57◦E. 90◦

2. One revolution is the same as:

A. 1 radB. 57 radC. π/2 radD. π radE. 2π rad

3. One revolution per minute is about:

A. 0.0524 rad/B. 0.105 rad/sC. 0.95 rad/sD. 1.57 rad/sE. 6.28 rad/s

4. If a wheel turns with constant angular speed then:

A. each point on its rim moves with constant velocityB. each point on its rim moves with constant accelerationC. the wheel turns through equal angles in equal timesD. the angle through which the wheel turns in each second increases as time goes onE. the angle through which the wheel turns in each second decreases as time goes on

5. If a wheel is turning at 3.0 rad/s, the time it takes to complete one revolution is about:

A. 0.33 sB. 0.67 sC. 1.0 sD. 1.3 sE. 2.1 s

6. If wheel turning at a constant rate completes 100 revolutions in 10 s its angular speed is:

A. 0.31 rad/sB. 0.63 rad/sC. 10 rad/sD. 31 rad/sE. 63 rad/s

7. The angular speed of the second hand of a watch is:

A. (π/1800) rad/sB. (π/60) m/sC. (π/30) m/sD. (2π) m/sE. (60) m/s

8. The angular speed of the minute hand of a watch is:

A. (60/π) m/sB. (1800/π) m/sC. (π) m/sD. (π/1800) m/sE. (π/60) m/s

9. A flywheel is initially rotating at 20 rad/s and has a constant angular acceleration. After 9.0 s it has rotated through 450 rad. Its angular acceleration is:

A. 3.3 rad/sB. 4.4 rad/sC. 5.6 rad/sD. 6.7 rad/sE. 11 rad/s

10. Ten seconds after an electric fan is turned on, the fan rotates at 300 rev/min. Its average angular acceleration is:

A. 3.14 rad/s^{2}B. 30 rad/s^{2}C. 30 rev/s^{2}D. 50 rev/min^{2}E. 1800 rev/s^{2}

11. A wheel rotates with a constant angular acceleration of π rad/s^{2}. During a certain time interval its angular displacement is π rad. At the end of the interval its angular velocity is 2π rad/s. Its angular velocity at the beginning of the interval is:

A. zeroB. 1 rad/sC. π rad/sD. π√2radsE. 2π rad/s

12. A flywheel rotating at 12 rev/s is brought to rest in 6 s. The magnitude of the average angular acceleration in rad/s2 of the wheel during this process is:

A. 1/πB. 2C. 4D. 4πE. 72

13. A phonograph turntable, initially rotating at 0.75 rev/s, slows down and stops in 30 s. The magnitude of its average angular acceleration in rad/s^{2} for this process is:

A. 1.5B. 1.5πC. π/40D. π/20E. 0.75

14. The angular velocity of a rotating wheel increases by 2 rev/s every minute. The angular acceleration in rad/s^{2} of this wheel is:

A. 4π2B. 2πC. 1/30D. π/15E. 4π

15. A wheel initially has an angular velocity of 18 rad/s. It has a constant angular acceleration of 2.0 rad/s^{2} and is slowing at first. What time elapses before its angular velocity is 18 rad/s in the direction opposite to its initial angular velocity?

A. 3.0 sB. 6.0 sC. 9.0 sD. 18 sE. 36 s

A. 2.0 rad/s^{2}B. −2.0 rad/s^{2}C. 3.0 rad/s^{2}D. −3.0 rad/s^{2}E. 6.0 rad/s^{2}

A. 2.0 rad/s^{2}B. −2.0 rad/s^{2}C. 3.0 rad/s^{2}D. −3.0 rad/s^{2}E. −6.0 rad/s^{2}

18. A wheel initially has an angular velocity of 18 rad/s but it is slowing at a rate of 2.0 rad/s^{2}. By the time it stops it will have turned through:

A. 81 radB. 160 radC. 245 radD. 330 radE. 410 rad

19. A wheel starts from rest and has an angular acceleration of 4.0 rad/s^{2}. When it has made 10 rev its angular velocity is:

A. 16 rad/sB. 22 rad/sC. 32 rad/sD. 250 rad/sE. 500 rad/s

20. A wheel starts from rest and has an angular acceleration of 4.0 rad/s^{2} The time it takes to make 10 rev is:

A. 0.50 sB. 0.71 sC. 2.2 sD. 2.8 sE. 5.6 s