4. The boy of mass 40 kg is sliding down the spiral slide at a constant speed such that his position, measured from the top of the chute, has components r = 1.5 m, 0 = = (0.6t) rad, and z = (-0.4t) m, where t is in seconds. Determine the magnitude of the resultant force the slide exerts on the boy at the instant t = 2 s. Neglect the size of the boy. Z Z r = 1.5 m