I just don't know what I'm doing wrong, I keep getting 21.82 again! Please help?!?

If an object is thrown in an upward direction from the top of a building 160 ft. high at an initial speed of 21.82 mi/h., what is its final speed when it hits the ground?(Disregard wind resistance. Round answer according to significant figures and do not reflect negative direction in your answer.
a)110
b)106
c)80

Question

I just don't know what I'm doing wrong, I keep getting 21.82 again! Please help?!?


If an object is thrown in an upward direction from the top of a building 160 ft. high at an initial speed of 21.82 mi/h., what is its final speed when it hits the ground?(Disregard wind resistance. Round answer according to significant figures and do not reflect negative direction in your answer.
a)110
b)106
c)80

anonymous · Answer

hmm.. can u show me how u keep getting that answer?

anonymous · Answer

So i keep getting 8.0 rounded to the closest tenth it should be distance/over time, but to be honest i would have mashy look at it

anonymous · Answer

alright, let me see if I can show you how I've been trying to figure it out

anonymous · Answer

ok so, scratch the 21.82 answer, I was plugging it in wrong, but is the answer 80 then?

anonymous · Answer

what is the value of g that u take?

anonymous · Answer

I used 9.8m/s2

anonymous · Answer

Im pretty sure its 8.0 but again i would wait for mashy to answer

anonymous · Answer

Its just that, that's not one of the choices. I am an online student, so I have no teacher. A lot of times, its really hard to learn physics by yourself. So its problems like this one, where I just don't know how to arrive at the answer. Im really bad with formulas because I don't always know where to plug things in. The choices on the program don't match that of which you are getting, its just really confusing

anonymous · Answer

yeah im online too, umm whats the formula your using

anonymous · Answer

The attached file is the formulas for the topic im on now. I've been trying a few of them, because I don't know which one is the proper one to use

anonymous · Answer

ill take a look one sec

anonymous · Answer

thats alot of equations ill try a few and tell you what i get your using 9.8 for g right?

anonymous · Answer

yeah because isn't g the acceleration due to gravity(9.8)

anonymous · Answer

haha.. g is 9.8 METERS PER SECOND square
but ur units are in FPS.. so you need to convert it into feet per second square..

anonymous · Answer

so its 32.15 feet/ second square!

anonymous · Answer

Are we done? 
Use m g h' = (1/2) m V^2 to go from initial velocity to
height above initial position.

Use m g h = (1/2) m v^2 to go from h = h' + 160 ft
to the velocity v at the ground, v.

anonymous · Answer

none of your answers are right and yet idk the right answer :(