Question

samantha threw an apple out of 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 takr the apple to hit the ground? round to the nearest hundredth.

Answer 1

Answer: 2.74 seconds

Step-by-step explanation:

Given: 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.

To find the time it took the apple to hit the ground.

When apple hits the ground, then the height of the apple above the ground will be zero.

Put y=0 in the given equation, we get

$-16t^2+120=0\\\Rightarrow16t^2=120\\\Rightarrow\ t^2=7.5\\\Rightarrow\ t=\pm\sqrt{7.5}\\\Rightarrow\ t=2.73861278753\approx2.74....\text{[Time is cannot be negative.]}$

Hence, it took 2.74 seconds to hit the ground.

Answer 2

To hit the floor means the height is 0.
-16t²+120=0
-16t²=-120
t²=7.5
t=2.74