The slider P moves inward by pulling a string (is not shown). The arm angular position is given in radians by theta = 0.8t-t^2/20 where t is time in seconds. the slider is at r=1.6 m when t=0 and thereafter it is drawn inward at a constant rate of 0.2m/s. find the magnitude and direction of the velocity and the acceleration of the slider at t=4sec.