Given that, mass of wheel, m=20kg Radius, R=30cm=30×10−2m Initial angular speed, ω0=80rpm=
80×2π
60
=
8π
3
rad∕s Angular displacement, θ=2π×( number of revolution) =2π×5=10πrad Final angular speed, ω=0 By equations of rotational kinematics. Angular acceleration, α=
ω2−ω02
2θ
Substituting the given values, we get α=
0−(
8π
3
)2
2×10π
rad∕s2 =−
16π
45
rad∕s2 Now, the tangential force will act opposite to the direction of rotation of wheel which will provide necessary retarding torque. ∴τ=Iα=FR ⇒F=
