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Bill borrows his dad's gun and when he gets outside he fires it straight up into the air. If the bullet left the gun at 400 m/s: How long does it take the bullet to reach its highest point.

I know that I have to use the acceleration of gravity which is 9.81 m/s2. Also, I suspect this question will use quadratic equations. This is what i tried.

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closed as off-topic by David Z Mar 30 '14 at 23:48

This question appears to be off-topic. The users who voted to close gave this specific reason:

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What have you tried? –  Draksis Mar 30 '14 at 23:39
user3175999, I'd suggest you take a look at our homework policy to see what sorts of questions are and aren't appropriate on this site, for future reference. –  David Z Mar 30 '14 at 23:49
i told you what i tried. –  user3175999 Mar 30 '14 at 23:53
@user3175999 You noted that the acceleration of gravity must be used in the solution, which is true. However, you need to provide detailed steps you took towards an answer to demonstrate that you've put forth at least some effort into solving the problem yourself. –  Draksis Mar 31 '14 at 0:04
I figured it out. The key is that the final velocity is zero. From there, the kinematic equations can be used. –  user3175999 Mar 31 '14 at 2:14

2 Answers 2

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The velocity decreases at $(9.81 m/sec)/sec$ Divide that into the starting velocity to find the time it takes the velocity to get to zero.

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Assume air resistance is 0 and that the bullet goes completely vertically. I don't see any reason to model it as a quadratic. Just normal kinematic equations.

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how would you do it. –  user3175999 Mar 30 '14 at 23:36

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