Question

Arianna kicks a soccer ball off the ground and into the air with an initial velocity of 42 feet per second. Assume the starting height of the ball is 0 feet. Approximately how long does it take until the soccer ball hits the ground again?

1.3 secs

2.6 secs

16.0 secs

27.6 secs

I think it's D, but I see a lot of people saying it's B?

Answer 1

Are you using this equation :
H(t) = -16t^2 + vt + s

?

Answer 2

plug the given info in the equation :
initial height = s = 0,
v = 42

Answer 3

H(t) = -16t^2 + 42t

Answer 4

set it equal to 0 and solve

Answer 5

H(0)=-16*0^2+42*0?

Answer 6

Sorry I disappeared.

Answer 7

@SolomonZelman @thomaster @iPwnBunnies

Answer 8

The ball will hit the ground when the height, H(t), is equal to 0

So when H(t) = 0

Plug 0 in for H(t) and solve for t


H(t) = -16t^2 + 42t

0 = -16t^2 + 42t

-16t^2 + 42t = 0

-2t(8t - 21) = 0


I'll let you finish

Answer 9

\(\bf \text{initial velocity}\\
h = -16t^2+v_ot+h_o \qquad \text{in feet}\\

\\ \quad \\

v_o=\textit{initial velocity of the object}\\
h_o=\textit{initial height of the object}\\
h=\textit{height of the object at "t" seconds}
\\ \quad \\ \quad \\

h = -16t^2+42t+0 \implies 0= -16t^2+42t+0\)