a) The initial angular speed is 209.3 m/s
b) The angular acceleration is 
c) The angular speed after 40 s is 139.7 rad/s
d) The wheel makes 1501 revolutions
Explanation:
a)
The initial angular speed of the wheel is

which means 2000 revolutions per minute.
We have to convert it into rad/s. Keeping in mind that:


We find:

b)
To find the angular acceleration, we have to convert the final angular speed also from rev/min to rad/s.
Using the same procedure used in part a),

Now we can find the angular acceleration, given by

where
is the initial angular speed
is the final angular speed
t = 60 s is the time interval
Substituting,

c)
To find the angular speed 40 seconds after the initial moment, we use the equivalent of the suvat equations for circular motion:

where we have


And substituting t = 40 s, we find

d)
The angular displacement of the wheel in a certain time interval t is given by

where


And substituting t = 60 s, we find:

So, the wheel turns 9426 radians in the 60 seconds of slowing down. Converting this value into revolutions,

Learn more about circular motion:
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