Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

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.

share|improve this question

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

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

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – David Z
If this question can be reworded to fit the rules in the help center, please edit the question.

    
What have you tried? –  Draksis Mar 30 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 at 23:49
    
i told you what i tried. –  user3175999 Mar 30 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 at 0:04
1  
I figured it out. The key is that the final velocity is zero. From there, the kinematic equations can be used. –  user3175999 Mar 31 at 2:14

2 Answers 2

up vote 0 down vote accepted

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.

share|improve this answer

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.

share|improve this answer
    
how would you do it. –  user3175999 Mar 30 at 23:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.