CrazCo Posted November 30, 2009 Share Posted November 30, 2009 I don't even know where to start, it's for calculus. If At one point a bullet is shot 1900ft straight into the air. Find the exit velocity (Vo). The height (H) after (T) seconds is H = VoT-16T^2. All I've done thus far is find the derivative. Am I on the right track? What should I do? Link to comment Share on other sites More sharing options...
timo Posted November 30, 2009 Share Posted November 30, 2009 Why have you taken the derivative and of what and with respect to which variable? If you know why you did so then you're probably close to the solution. Link to comment Share on other sites More sharing options...
CrazCo Posted November 30, 2009 Author Share Posted November 30, 2009 I did it because the derivative is velocity.. just set it to 0? Link to comment Share on other sites More sharing options...
timo Posted November 30, 2009 Share Posted November 30, 2009 It's really not my intent to piss you off or something like that but a) "because the derivative is velocity" is not an answer to any of the three questions I asked and b) the only sensible answer to your question whether to set it to zero or not (that is in agreement with the forum rules) is again "why so?". I mean, you must have an idea why you want to do so? If you feel like that you have an idea but find it hard to express: Finding something hard to explain to others is often a sign of not having understood it properly. So it really can be worth poking exactly such points. Link to comment Share on other sites More sharing options...
CrazCo Posted November 30, 2009 Author Share Posted November 30, 2009 the first derivative of something is velocity. the exit velocity is at time = 0 so by finding the derivative and setting it to 0 and isolating t you have the velocity when time is 0. you then replace that into the original equation and replace s with 1900. isolate the Vo and it's the answer. How is that not right? Link to comment Share on other sites More sharing options...
timo Posted November 30, 2009 Share Posted November 30, 2009 the first derivative of something is velocity. No. Counter example: The first derivative of velocity with respect to time is acceleration, not velocity. the exit velocity is at time = 0 ok. so by finding the derivative and setting it to 0 and isolating t you have the velocity when time is 0. No. When you set the velocity equal to zero and solve for time you get the time at which the velocity equals zero. It might be interesting to think about what that physically means (and how the whole motion look, physically). Link to comment Share on other sites More sharing options...
CrazCo Posted November 30, 2009 Author Share Posted November 30, 2009 I get it. Thanks! Link to comment Share on other sites More sharing options...
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