A slider P moves in the rotating slotted arm OA, controlled by a power screw as shown in the figure below. At the instant concerned: the arm is rotating anticlockwise about O with a constant angular velocity of 10 rad/s; the slider is 450 mm away from 0; the slider has zero total acceleration. For this instant, determine the acceleration of the slider along the screw, expressing your answer to one decimal place, as positive or negative noting the positive r direction shown, in units of m/s (but do not include the units in your answer).