At the instant shown, the 160-lb vaulter’s center of mass is 8.5 ft above the ground, and...

At the instant shown, the 160-lb vaulter’s center of mass is 8.5 ft above the ground, and the vertical component of his velocity is 4 ft/s. As his pole straightens, it exerts a vertical force on the vaulter of magnitude 180 + 2.8y2 lb. where y is the vertical position of his center of mass relative to its position at the instant shown. This force is exerted on him from y = 0 to y = 4 ft, when he releases the pole. What is the maximum height above the ground reached by the vaultcr’s center of mass?