Question

18. A ball is thrown upward from an 80-ft tower with an initial vertical speed of 40 ft/s. If air resistance is ignored, the ball's speed when it reaches the ground will be A. 67 ft/s. B. 130 ft/s. C. 120 ft/s D. 49 ft/s. E. 82 ft/s.

Answer 1

The maximum height reached by the ball is Use, 9.81 m/s^2 = 32 ft/s^2 h = u^2/2g = (40 ft/s)^2(32 ft/s^2) = 25 ft The total height of the ball when it was at maximum height is, H = 25 ft + 80 ft = 105 ft The velocity of the ball when it reaches the ground is, v = squareroot 2gH = squareroot 2(32 ft/s^2)(105 ft) = 81.97 ft/s almostequalto 82 ft/s Hence, the correct option is E