1. A disk rotates 90 degree in 10 seconds, what is its angular speed? A) 10 degr
ID: 2033331 • Letter: 1
Question
1. A disk rotates 90 degree in 10 seconds, what is its angular speed?
A) 10 degrees
B) 900 degrees
C) 90 degrees
D) 9 degrees
2. A disk rotates at 9 rad/s angular speed, a big standing on the disk with a distance 1.5m from its center, what is the linear speed of this bug as it rotates along with the disk?
A) 1.5 m/s
B) 6 m/s
C) .17 m/s
D) 13.5 m/s
3. The blades in a blender change the angular speed of its rotation from 100 rad/s to 40 rad/s in 4 seconds, what is the angular acceleration during this time?
A) 10 rad/s^2
B) -25 rad/s^2
C) 35 rad/s^2
D) -15 rad/s^2
Explanation / Answer
here,
1)
theta = 90 degree
time , t = 10 s
the angular speed , w = theta/t = D) 9 degrees
2)
w = 9 m/s
r = 1.5 m
the linear speed , v = r * w
v = 13.5 m/s
the linear speed is D) 13.5 m
3)
initial angular speed , w0 = 100 rad/s
final angular speed , w = 40 rad/s
t= 4 s
let the angular accelration be alpha
w = w0 + alpha * t
40 = 100 + alpha * 4
alpha = - 15 rad/s^2
the angular accelration is D) - 15 rad/s^2
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