Question

If a baseball player hits a baseball from 4 feet off the ground with an initial velocity of 64 feet per second, how long will it take the baseball to hit the ground? Use the equation h = -16t2 + 64t + 4.

A) 2 plus or minus square root of 17 end root over 2

B) quantity of 2 plus or minus square root of 17 all over 2

C)2 plus or minus 4 square root of 17

D) quantity of 16 plus or minus square root of 17 all over 2

Answer 1

\[-16t^2+64t+4=0\]and\[t=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\]

Answer 2

the equation is a quadratic

the 'standard' form for a quadratic is

\[ax ^{2}+bc+c=0\]
so compare that with
\[-16t ^{2}+64t+4\]

Answer 3

the ball hits the ground when h=0

(you can see that at time t=0 then h=4 (look at the equation when t=0))

There are 2 solutions - as given by the equation inD3xt3r's post

Answer 4

Only one wil be a positive value of t - the other represents the time when the ball WOULD'VE been at ground level if it had started there...

Answer 5

The right answer will be obtained by:\[t=\frac{-b-\sqrt{b^2-4ac}}{2a}\]

Answer 6

but there is no way for the OP to know that without you telling - she should solve for BOTH solutions and find the correct one...

Answer 7

Yes, but she'll find 2 different solutions, and one of them will be a negative time. And we know that a negative time don't exist.

Answer 8

Im still confused will t in the equation becom my x in the formula?

Answer 9

there IS a time before the measurement started.

IF for instance the ball was projected from ground level, but time was measured from the time it reached 4 ft high then the -ve time IS a valid solution.

The zero point for t is arbitrary ,a nd in most motion equations the -ve time solution is equally valid

Answer 10

x is just e 'normal' letter used for an unknown variable.

In this case the unbknown is time and is represented by t

SO - yes - you can swap t and x in these equations

Answer 11

OMG, I didn't see it. sry.