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?

- anonymous

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- terenzreignz

When it lands, what height does it have?

- terenzreignz

Wrong way to phrase it...
Let me rephrase....
How high is the ball when it lands?

- anonymous

4.9?

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## More answers

- terenzreignz

When it lands, is it 4.9 meters above the ground?

- anonymous

i have no idea

- anonymous

what do i have to do to get the answer?

- terenzreignz

Start with that... find the height of the ball as soon as it lands. It just takes a little intuition and visualization :)

- anonymous

-16

- terenzreignz

So... when the ball lands, it is 16 meters underground?

- anonymous

yupp

- anonymous

or no 16

- terenzreignz

16 means when the ball lands, it is 16 meters above the ground (in mid-air).
Does that seem reasonable?

- anonymous

no.

- terenzreignz

Then... what is reasonable?
When the ball lands, its height is...?

- anonymous

5f

- terenzreignz

What's f?

- anonymous

didnt mean to put tht srry

- terenzreignz

Well... you mean to tell me that when the ball *lands* it is 5 meters above the ground, then?

- anonymous

omg!! i really dont kno

- terenzreignz

Think... meditate... :P
Now...
how high is the ball when it LANDS...
how many meters above the ground is the ball when it LANDS...

- anonymous

hmmm 0?

- terenzreignz

Yes. Finally :P

- anonymous

yay!!!! that was easy lol

- terenzreignz

Of course, when the ball lands, it is on the ground.
Thus, it is 0 meters above the ground.

- terenzreignz

0 is not the answer. -.-

- terenzreignz

that's just a stepping stone...

- anonymous

oh ok wat next?

- terenzreignz

We need v and s.
We already have v, the initial velocity, 4.9

- terenzreignz

What's the initial height (s) ?

- anonymous

4.9^2

- terenzreignz

Are you guessing?
I strongly advise against it... it's too risky.

- terenzreignz

And no, the initial height is not \(\ 4.9^2\)

- anonymous

ok thnx for your help ill do the rest by myself :)
thnx

- terenzreignz

Are you sure? Well, if you're sure, post your answer here.

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