a) The angular velocity of the disk is 150 rpm (revolutions per minute). We can convert it into proper units, i.e. radiants per seconds, keeping in mind that:
[tex]1 rev = 2 \pi rad[/tex]
[tex]1 min = 60 s[/tex]
so the angular speed is
[tex]\omega = 150 \frac{rev}{min} = 150 \frac{2 \pi rad}{60 s} =15.7 rad /s[/tex]
b) The linear velocity is given by
[tex]v=\omega r[/tex]
since the radius is r=0.025 m, the linear velocity at the edge of the disk is
[tex]v= \omega r = (15.7 rad/s)(0.025 m)=0.39 m/s[/tex]
