A rotating wheel changes angular speed from 1800 rpm to 3000 rpm in 20 s. What is the angular acceleration assuming to be uniform? [KCET 2014]

We know that,   ω=2πnGiven,  n1=1800rpm,n2=3000rpm,Δt=20 s            ω1=2πn1=2π×180060=2π×30=60πrad/sSimilarly,    ω2=2πn2=2π×300060=2π×50=100πrad/sIf the angular velocity of a rotating wheel about an axis is changed by change in angular velocity in a time interval Δt,  then the angular acceleration of rotating wheel about that axis is given byα= Change in angular velbcity  Time interval =ω2-ω1Δt=100π-60π20=40π20=2πrads-2