allie_bear22
The height in meters of a projectile can be modeled by h = -4.9t^2 + vt + s where t is the time (in seconds) the object has been in the air, v is the initial velocity (in meters per seconds) and s is the initial height (in meters). A soccer ball is kicked upward from the ground and flies through the air with an initial vertical velocity of 4.9 meters per second. After how many seconds does it land approximately?
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terenzreignz
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When it lands, what height does it have?
terenzreignz
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Wrong way to phrase it...
Let me rephrase....
How high is the ball when it lands?
allie_bear22
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4.9?
terenzreignz
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When it lands, is it 4.9 meters above the ground?
allie_bear22
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i have no idea
allie_bear22
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what do i have to do to get the answer?
terenzreignz
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Start with that... find the height of the ball as soon as it lands. It just takes a little intuition and visualization :)
allie_bear22
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-16
terenzreignz
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So... when the ball lands, it is 16 meters underground?
allie_bear22
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yupp
allie_bear22
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or no 16
terenzreignz
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16 means when the ball lands, it is 16 meters above the ground (in mid-air).
Does that seem reasonable?
allie_bear22
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no.
terenzreignz
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Then... what is reasonable?
When the ball lands, its height is...?
allie_bear22
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5f
terenzreignz
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What's f?
allie_bear22
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didnt mean to put tht srry
terenzreignz
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Well... you mean to tell me that when the ball *lands* it is 5 meters above the ground, then?
allie_bear22
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omg!! i really dont kno
terenzreignz
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Think... meditate... :P
Now...
how high is the ball when it LANDS...
how many meters above the ground is the ball when it LANDS...
allie_bear22
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hmmm 0?
terenzreignz
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Yes. Finally :P
allie_bear22
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yay!!!! that was easy lol
terenzreignz
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Of course, when the ball lands, it is on the ground.
Thus, it is 0 meters above the ground.
terenzreignz
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0 is not the answer. -.-
terenzreignz
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that's just a stepping stone...
allie_bear22
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oh ok wat next?
terenzreignz
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We need v and s.
We already have v, the initial velocity, 4.9
terenzreignz
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What's the initial height (s) ?
allie_bear22
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4.9^2
terenzreignz
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Are you guessing?
I strongly advise against it... it's too risky.
terenzreignz
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And no, the initial height is not \(\ 4.9^2\)
allie_bear22
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ok thnx for your help ill do the rest by myself :)
thnx
terenzreignz
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Are you sure? Well, if you're sure, post your answer here.