What is the minimum speed a ball must be thrown upward if it is to reach a height of 11 feet?
A) 11 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 11 feet?
A) 11 ft/s 
B) ft/s 
C) ft/s 
D) 0 ft/s

Quizplus · Accepted Answer

The height h, in feet, of a ball thrown upward with an initial velocity v, in feet per second, after t seconds is given by the formula h=vt-16t^2. 
At the maximum height, the velocity becomes 0, which means that the ball stops at that instant and then starts to fall down. 
So, v^2-2gh=0, where g is the acceleration due to gravity, which is approximately 32 ft/s^2. 
Thus, solving for v gives v=sqrt(2gh). 
Plugging in h=11 and g=32, we get v=sqrt(2*32*11)=11.16 ft/s. 
Therefore, the correct answer is option C, 11.16 ft/s, rounded to the nearest hundredth.

What Is the Minimum Speed a Ball Must Be Thrown