1. Limited time only! Sign up for a free 30min personal 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!

How to calculate instantaneous acceleration if -->

  1. Jun 26, 2016 #1
    • Member advised to use the homework template for posts in the homework sections of PF.

    Sci1.PNG
    I tried but I can't. Sci1.PNG
     
  2. jcsd
  3. Jun 26, 2016 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

  4. Jun 26, 2016 #3
    First I used the formula dv/dt but I am used to have a ƒ(x) in the questions I usually did.
     
  5. Jun 26, 2016 #4

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Write dv/dt in terms of x and y, as defined in this question.
    What is the gradient at a point on a graph, a) in terms of algebra, and b) in terms of geometry?
     
  6. Jun 26, 2016 #5

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    +1

    It looks like this question is testing that you know what dx/dt and dv/dt mean in the real world.
     
  7. Jun 26, 2016 #6
    I am NOT getting it. Can you be a little more specific.
     
  8. Jun 26, 2016 #7

    Nidum

    User Avatar
    Science Advisor
    Gold Member

    Edit : Distorted plot corrected .
     
    Last edited: Jun 26, 2016
  9. Jun 26, 2016 #8

    Nidum

    User Avatar
    Science Advisor
    Gold Member

    dydx mk2mk2.jpg
     
    Last edited: Jun 26, 2016
  10. Jun 26, 2016 #9

    rcgldr

    User Avatar
    Homework Helper

    There's a conflict in the figure, t2 is stated as being 3.8, but shows as 4.0 in the figure. There's insufficient information to determine instantaneous acceleration without more sample points or a limitation on the formula for acceleration versus time. If the figure was more accurate, the multiple sample points could be used to generate a function for position versus time, and then velocity and acceleration versus time. For example, the graph could be a hyperbola, in which case acceleration approaches zero as time and distance increase, or the graph could be a parabola, in which case acceleration is constant, although the graph seems to be closer to being a hyperbola.
     
    Last edited: Jun 26, 2016
  11. Jun 26, 2016 #10

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    Sorry I disagree. I think that's deliberate.

    It states the velocity at t=3.8 seconds is 130m/s and asks you to calculate the acceleration at t2=4.0 seconds. The graph gives you enough data to calculate the velocity at t2=4.0. So you have the velocities at two points a known time apart.

    The accuracy might not be great but you can calculate an answer.
     
  12. Jun 26, 2016 #11

    rcgldr

    User Avatar
    Homework Helper

    I wasn't paying attention to the limited choices of possible answers, so the accuracy doesn't need to be that great. There's no information after t = 4.0, so what's being calculated is the average acceleration from t = 3.8 to t = 4.0, not the instantaneous acceleration at t = 4.0. Based on the graph and the data, the acceleration is decreasing with time, instantaneous acceleration at t = 4.0 would be less.
     
    Last edited: Jun 26, 2016
  13. Jun 26, 2016 #12

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    @Hardikph , I don't know if you've been able to follow the discussion between CWatters and rcgldr.
    You are told the velocity at t=3.8s, and there is enough information in the graph to find it at t=4s. Can you see how to deduce that second velocity? Having got the two velocities, can you see how to estimate the acceleration?
     
  14. Jun 28, 2016 #13
    Now I Understand. Thank You guys.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How to calculate instantaneous acceleration if -->
Loading...