Answer:
The pebble will hit the ground 8.29 second after it is thrown.
Step-by-step explanation:
Given that,
The height of the pebble after t seconds is given by the equation
h= -16t²+24 t+900.
When the pebble hit the ground, the height of the pebble will be zero.
So putting h=0 in the given equation.
0 = -16t²+24 t+900
⇒-4(4t²-6t-225)=0
⇒4t²-6t-225=0
Applying quadratic formula [tex]t=\frac{-b\pm\sqrt{b^2-4ac}}{2a}[/tex], here a=4, b= -6 and c= -225.
[tex]\therefore t=\frac{-(-6)\pm\sqrt{(-6)^2-4.4.(-225)}}{2.4}[/tex]
⇒ t = 8.29, -6.79
Since time can not negative.
∴t=8.29 seconds.
The pebble will hit the ground 8.29 second after it is thrown.
