The slider P can be moved inward by means of the string S, while the slotted arm rotates about point O. The angular position of the arm is given by θ = 0.8t − t2/20 , where θ is in radians and t is in seconds. The slider is at r = 1.6 m when t = 0 and thereafter is drawn inward at the constant rate of 0.2 m/s. Determine the magnitude and direction (expressed by the angle α relative to the x-axis) of the velocity and acceleration of the slider when t = 4 s.
