Question
A wheel starting from rest is uniformly accelerated at 2 rad\sec^2 for 20s.It is allowed to rotate uniformly for next 10s and finaly brought to rest in next 20s.Find total angle rotated by wheel ( in radian).
Joshi sir comment
ω = 0 + 2(20) = 40 (according to rotational equation ω = ω0 + αt)
and θ = 0 + 1/2(2)(20)2 = 400 radian
in middle uniform part angle rotated = 40*10 = 400 radian
and since acceleration in first part and retardation in last part are equal so angle rotated in last part = 400 radian
total = 1200 radian