A projectile is fired directly upward with an initial velocity 144 ft/secs. Its height s(t) in feet above the ground after t seconds is given by s(t) = 144 - 16t^2. a) what are the velocity and acceleration after t sec? b) after 3 sec? c) What is the maximum height? d) when does it strike the ground?

Question

anonymous · Answer

Ah, initial conditions..:-)

amistre64 · Answer

this is wrong

amistre64 · Answer

s(t) = 144 - 16t^2

amistre64 · Answer

should be:  s(t) = 144t - 16t^2

anonymous · Answer

yes, he did the v(t) and asked a question.....

anonymous · Answer

This is the whole question that 'm talking about...

amistre64 · Answer

i know, but initial velocity is not the same as initial height in the equation

amistre64 · Answer

s(t) = Gt^2 + Vt + H

amistre64 · Answer

s(t) = -16t^2 +144t + 0

anonymous · Answer

good eye!

amistre64 · Answer

bad back tho ;)

anonymous · Answer

lol!

amistre64 · Answer

s(t) = -16t^2 +144t

v(t) = -32t + 144

a(t) = -32

amistre64 · Answer

v(3) = -32(3) + 144
       = -96 + 144

a(3) = -32

anonymous · Answer

morning joe
don't forget maximum height right?

amistre64 · Answer

the max height is at v(t) = 0

v(t) = -32t + 144 = 0; when t = 144/32

s(9/2) = -16(9/2)^2 +144(9/2)

anonymous · Answer

SCHOOL!!!
@everyone morning :)

amistre64 · Answer

it strikes that ground again after another 9/2 secs so:

2(9/2) secs

amistre64 · Answer

see how easy that is when you give all the info to begin with ;)

amistre64 · Answer

any thoughts?  or corrections?

anonymous · Answer

where is your spirit of adventure!? doing a problem with half the info needed is exciting and fun! lol

amistre64 · Answer

oh it is... it is.  but, there are times in the morning, you know, when the sun is barely peeking over the water crestnuts, and you gotta wonder to yourself, where did I leave me keys?

anonymous · Answer

lolol

anonymous · Answer

what is maximum height?

amistre64 · Answer

s(9/2) = -16(9/2)^2 +144(9/2)

amistre64 · Answer

the max height is when the thing stops moving up and starts to move down; so its velocity is at 0

v(t) = -32t + 144 = 0 when t = 144/32 = 9/2

anonymous · Answer

oh okay that's right thank you very much....

amistre64 · Answer

youre are quite welcome :)

amistre64 · Answer

im outta stickers but I got some of these:  ♫♫♫

anonymous · Answer

cool u r truly a legend hehehe.

anonymous · Answer

can is ask another question? cause i'm going to have my recitation tommorow?