Question

need a check A DOG IS FIRED VERTICALLY INTO THE AIR FROM A CANNON, WITH A VELOCITY OF 146FT/SEC. what is the altitude of the dog after 4 sec. and after 5.125 secs.? I GOT 4sec=584ft and 5.125sec.=748 ft

Answer 1

ft means -16t^2

initial velocity is 146; and initial height is ...negligible

Answer 2

\[h(t) = -16t^2+146t\]
right?

Answer 3

my notes gives me the formula 16t^2+Vot+So thats the same thing rite? u just plugged 0 for So?

Answer 4

I plugged 0 for So; but your notes need to have the "-16t^2" or else you get wrong results

Answer 5

at t=4; this is 328

Answer 6

ohhh i forgot the negative!!!

Answer 7

yeah, it helps when gravity actually pulls you back ;)

Answer 8

once again you've saved the day!!! :)

Answer 9

the value I get for 5.125 is 328 also; but I dont know if that means we hit the bend, or if its to small for my calculator to go any further

Answer 10

thats the same thing i got and im using a TI-84..DOES THAT MEAN MY ANSWER IF OFF??

Answer 11

the answer you gave above is off :)

but I just graphed it on me ti83plus and it shows its just on opposite sides of the bend; so its good

328 is the answer for both t=4 and t=5.125

Answer 12

OK THANKS!!!

Answer 13

one way to tell is to see if the vertex is exactly between 4 and 5.125

-32t +146 = 0 at t = 146/32

146/32 -n = 4
146/32 +n = 5.125
------------------
146/16 = 9.125 ? its true

Answer 14

ITS ALSO ASK HOW LONG UNTIL THE DOG LANDS I DNT EVN KNOW HOW TO BEGIN THAT ONE?

Answer 15

when the dog lands; h = 0 again;

Answer 16

but, the vertex tells us how long half the trip takes :)

so, landing time will take twice as long as it takes to reach the vertex.

vertex is at t = 146/32 right? now double it

Answer 17

should be 9.125 ...

Answer 18

i dnt understand? u just added the two times?

Answer 19

dbk chk that tho

Answer 20

not really adding the 2 times

but we know there is no forward momentum, since the dog is shot straight up; so the time it takes to reach the full height is the same amount of time it takes to fall back down to the ground right?

Answer 21

the 'vertex' is the point where it reaches it full height; so just double the time it takes to reach the vertex

Answer 22

since the vertex is half way between 4 and 5.125; add them together and divide by 2; then double it

Answer 23

\[\frac{4+5.125}{2}*2 = 4+5.125=9.125\]

Answer 24

ok thanx agin! well off to this algebra class!:( ttyl!!

Answer 25

Ciao bella ;)

Answer 26

Mon dieu, poor dog.