4. The 4-pound smooth particle is moved around by the forked rod, around the horizontal path in the shape of a roulette, r=(1 + cos theta ) ft, and theta = (0.5t2) rad, where t is in seconds. The fork and the path each contact the particle on one side only. Determine the force which the rod exerts on the particle when t = 1s.

Fig: 1

Fig: 2