Which equation would best help solve the following problem?

Hideki throws a baseball ball upward with an initial velocity of 12 meters/sec. When he throws the ball, it is two meters above the ground. How long will it take the ball to hit the ground?

–16t^2+ 12t + 2 = 0
–4.9t^2 + 12t + 2 = 0
–4.9t^2 + 12t = 2
4.9t^2 + 12t + 2 = 0

Question

Which equation would best help solve the following problem?

Hideki throws a baseball ball upward with an initial velocity of 12 meters/sec. When he throws the ball, it is two meters above the ground. How long will it take the ball to hit the ground? 


       –16t^2+ 12t + 2 = 0
       –4.9t^2 + 12t + 2 = 0
       –4.9t^2 + 12t = 2
       4.9t^2 + 12t + 2 = 0

whpalmer4 · Answer

The formula for the height in such a problem is 

$$h(t) = -\frac{1}{2}gt^2 + v_0 t + h_0$$where $g=9.8$ if doing a problem in metric units or $g=32$ if doing a problem in US units.  $v_0$ is the initial velocity, with a positive number corresponding to the projectile going up.  $h_0$ is the initial height from which it is launched, again with a positive number corresponding to a positive height.