A ball is thrown downward from the top of a 190​-foot building with an initial velocity of 21 feet per second. the height of the ball h after t seconds is given by the equation h equals negative 16 t squared minus 21 t plus 190. how long after the ball is thrown will it strike the​ ground?

To solve this problem you must apply the proccedure shown below:

 1- You have the following information give in the problem above:

 - The ball is thrown downward from the top of a 190​-foot building with an initial velocity of 21 feet per second.
- The height of the ball h after t seconds is given by this equation: h=-16t²-21t+190.

 2- h=0 when the ball strikes the ground, then you have:

 -16t²-21t+190=0

 3. When you solve the quadratic equation shown above, you obtain:

 t=2.85 seconds

 The answer is: 2.85 seconds.