Can someone please check my work on this math question? please? I'll fan and give a medal!!

Question

abbycross167 · Answer

18.   A tennis ball is launched with an initial velocity of 24.5 m/s from the edge of a cliff that is 117.6 meters above the ground. Which quadratic equation could be used to correctly determine when the ball will hit the ground:
4.9t2 + 24.5t + 117.6 = 0

-4.9t2 - 24.5t + 117.6 = 0

-4.9t2 + 24.5t - 117.6 = 0

4.9t2 + 24.5t - 117.6 = 0

-4.9t2 + 24.5t + 117.6 = 0

abbycross167 · Answer

my answer is -4.9t2 + 24.5t + 117.6 = 0

zzr0ck3r · Answer

why?

zzr0ck3r · Answer

is this for a calc class?

whpalmer4 · Answer

the equation of vertical position for something launched from initial height $h_0$ with vertical velocity $v_0$ and acceleration due to gravity $g$ will be

$$h(t) = -\frac{1}{2}gt^2 + v_0 t + h_0$$

Your answer is correct, as $g$ is usually taken as $\approx 9.8 \text{ m/s}^2$ and a positive value for $v_0$ means the ball is initially traveling upwards.

zzr0ck3r · Answer

From a math standpoint, we know the derivative give velocity. 

So the derivative needs to be something that we plug in 0 and get out 24.5

obviously the constant term is 117.6

do yes :)

abbycross167 · Answer

thank you very much!!