15-47. The free-rolling ramp has a weight of 120 lb. The crate whose weight is 80 lb sli...

15-47. The free-rolling ramp has a weight of 120 lb. The crate whose weight is 80 lb slides from rest at A, 15 ft down the ramp to B. Determine the ramp's speed when the crate reaches B. Assume that the ramp is smooth, and neglect the mass of the wheels.