Question

Samantha threw an apple out of a window from the tenth floor of her apartment building.The equation y=-16t^2+120 can be used to represent the fruits height above the ground, where t represents time, in seconds, after she threw the Apple. How long did it take the Apple to hit the ground?

Answer 1

the awnser your looking for is 2. something seconds 

Answer 2

If the apple is on the ground, then the height y is 0. To find t, just plug in 0 for y:

`0=-16t^(2)+120`

`-120=-16t^(2)`

`t^(2) =7.5`

`t=2.74`

So the answer is 2.74 seconds.

Note that taking the square root of 7.5, mathematically, gives you both 2.74 and -2.74. But because we know that time did not go backwards, only the positive value for t was considered.