Question

A boy standing on a 64 foot cliff drops a coin off the cliff. If the equation of the height h of the coin t seconds after it drops is h = -16t2 + 64, about how many seconds will the coin take to reach the bottom of the cliff?
A. 1 second
B. 1.5 seconds
C. 2 seconds
D. 2.5 seconds

Answer 1

okay what is the height of the bottom of the cliff?

Answer 2

lets go over this together.

Answer 3

probably 64!

Answer 4

try again.

Answer 5

haha :O ok ya lets go over it.

Answer 6

you can almost see that 2 squared is 4, and 4 * 16 = 64

Answer 7

the equation states that h is the height of the coin t seconds after it is dropped. You are asked to find when it reaches the bottom. So what is the height of the bottom?

Answer 8

the cliff is 64 ft. right? lol cuz u said whats the height of the bottom of the cliff
i think

Answer 9

yes, I know what I asked. So, answer me, what do you think the height of the bottom of the cliff is?

Answer 10

64!

Answer 11

if I am 6 feet high, how high is the bottom of my feet from the ground?

Answer 12

ok uhmm blonde moment rite now how bout 16?

Answer 13

0

Answer 14

YEAAH

Answer 15

haha wow blonde moment

Answer 16

throw h=0 in and solve for t!

Answer 17

Yes!. so the moment the coin touches the bottom of the cliff, it is 0 feet high from the ground.

Answer 18

rite.

Answer 19

craig is trying to rush through it lol

Answer 20

so equate h to 0 and solve the equation, that is,
0 = -16t^2+64

Answer 21

ah! ok one moment keep typing watever ur typing.

Answer 22

or, 16 t^2 = 64. or t^2 = 4 or t = +2 or -2. Since time cannot be negative, t = +2. So it takes 2 seconds to reach the bottom.

Answer 23

OH!!!! ok ok

Answer 24

that makes sense! (: thx!! xD

Answer 25

okay great! you are welcome.