1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple differentiation question

  1. Apr 24, 2008 #1
    helicopter moves vertically. Height above start point = y

    height at t seconds =
    y= (1/4)t^4 -26t^2 + 96t t = between 0 and 4
    differentiate to find velocity = t^3 + 52t + 96
    acceleration = 3t^2-52

    thats part 1 of question done, easy.

    Verify that y has a stationary value when t = 2 determine whether it is min/max value.

    i can put this into 3t^2-52t+96 and find out that it is.

    but how is it min/max

    nevermind : i put it into acceleration and find out if acceleration is more or less than the value i got for velocity. If it's less i know that the thing will never accelerate again after this given time. so it would be a maximum. Where as if it was more than the value i got for velocity i know that the object would be able to accelerate again, which is minimum.. right?
  2. jcsd
  3. Apr 24, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    No. For one thing you've got some scrambled formulas in your post, but assuming they are just typos, then if you did everything correctly you should have found v=0 at t=2. That's what a 'stationary' point means. Now check acceleration at t=2. What sign is it? What does that have to do with it being a min or a max?
  4. Apr 24, 2008 #3
    At a stationary point the velocity is 0, so you can just compare the acceleration with 0.
    if the acceleration is negative, you know there is a local maximum.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Simple differentiation question
  1. Simple trig question (Replies: 2)