Answer:
a) -1.57 rad/s²
b) 800 revolutions
Explanation:
a)In here you can use the equations of velocity as if it were a linear movement. In this case:
wf = wo + at
wo is the innitial angular velocity, that we can get this value using the fact that a revolution is 2π so:
wo = 20 * 2π = 125.66 rad/s
We have the time of 80 seconds, and the final angular speed is zero, because it's going to a rest so:
0 = 125.66 + 80a
a = -125.66 / 80
a = -1.57 rad/s²
b) In this part, we will use the following expression:
Ф = Фo + wo*t + 1/2 at²
But as this it's coming to rest then:
Ф = 1/2at²
solving we have:
Ф = 0.5 * (-1.57)*(80)²
Ф = 5,024 rad
Ф = 5024 / 2π
Ф = 800 revolutions
