physics equation help?? vertical motion?

Question

the equation is just like a quadratic.
Initial velocity= -50m/s
HOW LONG DOES IT TAKE TO REACH THE -750 METERS MARK???

Answer 1

Remember that distance is affected by the initial velocity, and gravity.

d = vt + 1/2at^2
-750 = -50t + 1/2 * -9.8 * t^2

For a quadratic equation, the equation must equal 0.
0 = -4.9t^2 - 50t + 750

Once you have the quadratic equation set up, plug in the quadratic formula:
t = (-b +/- (b^2 - 4ac)^1/2)/2a
t = (50 +/- (2500 + 14700)^1/2 / -9.8
t = -5.102 +/- -13.383
t = -18.485 or 8.281 - ignore the negative answer.

t = 8.281 sec (solution!)

Check:
-750 = -50t + -4.9t^2
-750 = -414.05 + -336.02
-750 = -750.06 (close enough...)