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Mathematics
OpenStudy (anonymous):

I am stuck on a couple of questions and need some help please... Here is the first one... If a stone is tossed from the top of a 350 meter building, the height of the stone as a function of time is given by h(t) = -9.8t2 – 10t + 350, where t is in seconds, and height is in meters. After how many seconds will the stone hit the ground? Round to the nearest hundredth’s place; include units in your answer.

OpenStudy (anonymous):

my brain is beginning to shut down it feels like ive been working on this test all day its my final exam n im stuck on 3 problems that i cant figure out

OpenStudy (anonymous):

Sub 350 for h(t) and solve the quadratic in t....

OpenStudy (anonymous):

If the stone hit the ground, h(t) = 0..

OpenStudy (anonymous):

Lol, yes, I was reading it backwards...

OpenStudy (anonymous):

Forget sub, solve the quadratic with h(t)=0

OpenStudy (anonymous):

i got kicked off but i am not so sure that i understand it still

OpenStudy (anonymous):

If you look at h(t) and set t= 0 u get 350, which is right, the stone starts at 350. The flip side, as Denebel pointed out, is that when it lands, h(t) = 0 = -9.8t2 – 10t + 350 so u just solve this quadratic (u will get 2 answers, one of which will be obviously wrong and discard it).

OpenStudy (anonymous):

h(t) describes the height of the stone in terms of t. When t=0, h(t) will equal 350, which is where the stone starts. So you want to find out how long it takes for the stone to hit the ground; in other words, when the height of the stone = 0. Therefore, h(t) = 0, and you solve for t. Estudier mentions that you will have 2 answers because of the quadratic formula. You will notice that one of the answer is wrong because it will have a negative sign or something like that, which is impossible because time cannot be a negative number. Your answer will be the positive number.

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