How Do You Solve Kinematics Problems Involving Quadratic Equations?

[Falinox]

Homework Statement

http://i754.photobucket.com/albums/xx183/reddiesel08/Phyque.jpg


2. The attempt at a solution
∆x = ∆x
v₀ + .5(a)(t²) = v(t)
.5(9.8)t² = 35t
4.9t² - 35t = 0 Using the quadratic formula I get
t = 7.95 sec

∆x = v(t)
35(7.95) = 278.25m

Need help setting up and solving the problem, thanks in advance to anyone willing to help :)

 

[SammyS]

35/4.9 ≈ 7.143 s.

Why use the quadratic formula? -- although it should give the right answer. (35 ± √(35²-0) )/(2(4.9))

 

[SteamKing]

You've calculated the distance the ball travels from the drop point to the point where it passes superman. The problem however asks you determine how far above the sidewalk the ball is when it passes superman.

 

[Falinox]

Thanks everyone! I was able to figure it out.