Question

s(t) = -16 t^2 + 80 t

The rocket is traveling down at a velocity of 60 fps at what time?

Answer 1

calculus

Answer 2

s'(t)=v(t)=-32t+80

Answer 3

so 60=-32t+80
32t=20
t=20/32 s

Answer 4

t=20/32 is the answer?

Answer 5

thats wrong

Answer 6

well 20/32 is the fraction, 0.625 seconds is what I got,

Answer 7

I didn't have a calculator on hand, sorry if that's also wrong

Answer 8

i know but I plugged it and it said it was wrong

Answer 9

are you sure you posted the question correctly, or is there any other information, or unit conversion to be done?

Answer 10

if not, i'm sorry I don't think i can help

Answer 11

heres everything i know:

Answer 12

The height of a rocket launched from the ground is given by the function s(t) = -16 t^2 + 80 t,
where s is in feet above ground and t is in seconds.

After 3 seconds, the rocket is 96 feet above ground.

After 3 seconds, the rocket is traveling at a velocity of -16 feet per second.



The rocket is traveling down at a velocity of 60 fps at what time?
0.625 Incorrect: Your answer is incorrect.

Answer 13

ah, okay hold on here

Answer 14

-60=-32t+80
32t=140
t=140/32
t=4.375 seconds

Answer 15

the time i gave you originally was, the time it took to go from the top of it's flight (0fps) to 60fps in the downward direction, so not enough information was given originally.

Answer 16

that should be correct now

Answer 17

ok lets see....

Answer 18

yeah its right thank you very much

Answer 19

so how did you find it?

Answer 20

so I can understand for another question

Answer 21

well you know that v(t) = s'(t)
and you know how to do calculus right?

Answer 22

deriv of t = v

Answer 23

not quite..
ds/dt=v(t)

Answer 24

so the deriv or ds/dt = the velocity of t

Answer 25

so the derivative of s with respect to t is the velocity in terms of t
..in words..

Answer 26

ok

Answer 27

kinda the same thing i said

Answer 28

basically if you have s(t) and you want velocity you will do s'(t) by calculus methods which you should know how to do, if you're taking this class. then the acceleration function is v'(t) or s''(t) if you need to find that

Answer 29

in this question since they said the velocity was -60 you can put that in the equation where v(t) is because -60 fps is the v(t) just like the acceleration was -32fps or v'(t)

Answer 30

whats the difference between v prime of (t) and the second deriv of (t)

Answer 31

which is gravity in america.. aha. crazy americans.

Answer 32

you would never say the second derivative of (t) it would be worded as the second derivative of s(t) or s''(t) or s double prime of t, and that is the acceleration function of t
so s''(t) = v'(t) = a(t)

Answer 33

oh ok

Answer 34

hey I just started this class so we havent gotten that far

Answer 35

t is always what the function is with respect to, it is the variable you are measuring, you are not deriving it, you are deriving in terms of it

Answer 36

and that's fine! calculus isn't an easy concept to grasp but when you do.. boy i tell ya. good times.. aha.

Answer 37

lol

Answer 38

is this highschool?

Answer 39

or university

Answer 40

no college im attending u of maryland