The 5-lb collar slides on the smooth rod, so that when it is at A it has a speed of 10 ft/...

The 5-lb collar slides on the smooth rod, so that when it is at A it has a speed of 10 ft/s. If the spring to which it is attached has an unstretched length of 3 ft and a stiffness of k = 10 lb/ft, determine the normal force on the collar and the magnitude of the acceleration of the collar at this instant.