David drops a ball from the top of a building with a height of 64 feet.
The height (h) of the ball, in feet, after (t) seconds can be found using
the formula h=-16° +64. How long will it take the ball to reach the
ground?
A)3 sec
B)2sec
C)1 sec
D)none

It says, in not so may words, that the object was dropped under the influence of gravity from a height of 64 feet. When it hits, the ground, it will not be above ground at all anymore...it will be ON the ground and have a height of 0. Therefore, if we set the position function equal to 0 and solve for t, we are finding out how long it will take for the object to hit the ground.

[tex]0=-16t^2+64[/tex] and

[tex]16t^2=64[/tex] and

[tex]t^2=4[/tex] and

t = 2

It takes 2 seconds for the object to hit the ground from 64 feet up.

David drops a ball from the top of a building with a height of 64 feet. The height (h) of the ball, in feet, after (t) seconds can be found using the formula h=-16° +64. How long will it take the ball to reach the ground? A)3 sec B)2sec C)1 sec D)none

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David drops a ball from the top of a building with a height of 64 feet.
The height (h) of the ball, in feet, after (t) seconds can be found using
the formula h=-16° +64. How long will it take the ball to reach the
ground?
A)3 sec
B)2sec
C)1 sec
D)none