To find the angular velocity of the body at t = 20s, we need to differentiate the angle of rotation function φ(t) with respect to time.
Given: φ(t) = 0.1t^2 - 0.5t + 0.2
To differentiate this function, we can use the power rule for differentiation:
dφ(t)/dt = d/dt (0.1t^2 - 0.5t + 0.2) = 0.2t - 0.5
Substituting t = 20s into the derived expression, we have:
dφ(t)/dt = 0.2 * 20 - 0.5 = 4 - 0.5 = 3.5 rad/s
Therefore, the angular velocity of the body at t = 20s is 3.5 rad/s.