Answer:
2.28 s
Explanation:
Let g = 9.8 m/s2 and neglect air resistance. The box of sand with an initial velocity of 4.2m/s in free fall would yield the following equation of motion
[tex]s = v_0t + gt^2/2[/tex]
[tex]35 = 4.2t + 9.8t^2/2[/tex]
[tex]4.9t^2 + 4.2t - 35 = 0[/tex]
[tex]t= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}[/tex]
[tex]t= \frac{-4.2\pm \sqrt{(4.2)^2 - 4*(4.9)*(-35)}}{2*(4.9)}[/tex]
[tex]t= \frac{-4.2\pm26.53}{9.8}[/tex]
t = 2.28 or t = -3.14
Since t can only be positive we will pick t = 2.28 s
