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Question :
6. A ceiling fan turned and reaches an angular speed : 2102150

6. A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned off and coasts to a stop in an additional 40 s. The ratio of the average angular acceleration for the first 20 s to that for the last 40 s is which of the following?

A. 2

B. 0.5

C. -0.5

D. -2

7. A 0.30-m-radius automobile tire rotates how many rad after starting from rest and accelerating at a constant 2.0 rad/s^{2} over a 5.0-s interval?

A. 12.5 rad

B. 25 rad

C. 2.0 rad

D. 0.50 rad

8. A fan blade, initially at rest, rotates with a constant acceleration of 0.025 rad/s^{2}. What is its angular speed at the instant it goes through an angular displacement of 4.2 rad?

A. 0.025 rad/s

B. 0.11 rad/s

C. 0.46 rad/s

D. 1.2 rad/s

9. A fan blade, initially at rest, rotates with a constant acceleration of 0.025 rad/s^{2}. What is the time interval required for it to reach a 4.2-rad displacement after starting from rest?

A. 1.8 s

B. 2.0 s

C. 16 s

D. 18 s

10. A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned off and coasts to a stop in 40 s. In the one minute of rotation, through how many revolutions did the fan turn?

A. 20

B. 60

C. 0

D. 600