Question

An object is thrown down towards the ground from the top of a 1100ft tall building with an initial velocity of -20 feet per second. Given that the acceleration due to gravity of the object is a constant -32 feet per second per second, determine how far above the ground the object is six seconds after being thrown.

Answer 1

Keep getting the wrong answer, that it is below the ground

Answer 2

Did you use the top of the cliff/building as "0" ? If so you should get a negative answer, though I'll double check your work.

Answer 3

Nope,1100

Answer 4

Your equation to describe the trajectory of the object is something like
\[f(x)=20t-32t^2\]
or is it
\[f(x)=20t-16^2\]

Answer 5

*16t^2 for the 2nd one

Answer 6

for my function i thought -20t-32t^2+1100

Answer 7

The equation that describes the motion is
\[f(x)=-20t-16t^2\]
I'm pretty sure you don't have the 1100 in there, though you will use it later to find the height.
You use "-16t^2" instead of "-32t^2" because the -32 value is -32 feet per second per second, or second squared, but to account for that, we just use -16 feet.
If you will take physics, you'll learn the reason behind this and the equation it's given in, but let's continue.

Answer 8

To first find the vertical distance the ball travels in 6 seconds, we just plug in 6 for "t" in our equation
\[f(x)=-20t-16t^2\]
and we get ______ as our answer?

Answer 9

404

Answer 10

Final answer.

Answer 11

I just Dont Understand why the -32^2 turns into -16t^2. Does this have to do with integrals?

Answer 12

your model should be h(t) = -16t^2 - 20t + 1100.

Answer 13

no, derivatives...

Answer 14

k... I get 404 ft after 6 seconds

Answer 15

Thank you so much

Answer 16

That answer seems to be correct

Answer 17

No problem :)

Answer 18

Do you believe this answer is correct

Answer 19

Wait. Is the answer 404 after plugging it in to
\[f(x)=-20t-16t^2+1100\]
or just \[f(x)=-20t-16t^2\]

If you got 404 after plugging into the 1st one, you need to subtract 404 from 1100, if you got 404 from using the second, then that is your final answer.

Answer 20

im looking for the height off of the ground after 6 seconds

Answer 21

h(t) refers to the height off the ground

Answer 22

Right, so if you used the first equation, you would only have found the distance traveled after 6 seconds, which you would have to subtract from the building height.
If you used the second equation that @dpanlc showed you, then it is correct.