What is the minimum speed a ball must be thrown upward if it is to reach a height of 13 feet?
A) 13 ft/s
B) ft/s
C) ft/s
D) 0 ft/s

Question

What is the minimum speed a ball must be thrown upward if it is to reach a height of 13 feet?
A) 13 ft/s 
B) ft/s 
C) ft/s 
D) 0 ft/s

Quizplus · Accepted Answer

The minimum speed a ball must be thrown upward in order to reach a height of 13 feet is the same as the speed it would be traveling right as it hits the ground. Using the formula vf^2 = vi^2 + 2ad where vf=0 (at the highest point), vi is the initial velocity, a is the acceleration due to gravity (-32 ft/s^2), and d is the distance traveled (13 feet), we can solve for vi.

0^2 = vi^2 + 2(-32)(13)
0 = vi^2 - 832
vi^2 = 832
vi = 28.84 ft/s

Since the ball is traveling downward when it hits the ground, the speed it would be traveling right before it hits the ground would be the opposite of the initial velocity, or 28.84 ft/s. Therefore, the minimum speed that the ball must be thrown upward is 28.84 ft/s or approximately 11.11 m/s, which is closest to choice C (11.11 ft/s or 3.39 m/s).

What Is the Minimum Speed a Ball Must Be Thrown