Answer
1.08 s
Work Step by Step
Let up be the positive direction:
$x=ut+\frac{1}{2}at^{2}$
$(-3.00)=(2.50)t+\frac{1}{2}(-9.8)t^{2}$
$4.9t^{2}-2.50t-3.00=0$
Using quadratic formula:
$t=\frac{-(-2.50)±\sqrt {((-2.50)^{2}-4(4.9)(-3.00)}}{2(4.9)}$
$t\approx1.08$ or $t\approx-0.57$
$t\approx1.08\; s$ since $t\gt0$
