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!

A Coordinates and Interval Question

  1. Jan 15, 2010 #1
    1. The problem statement, all variables and given/known data
    During a 4.95 s interval, a particle's coordinates change from x = 10.4 m, y = 4.95 m to x = 31.5 m, y = -4.95 m. Assuming the particle's velocity is constant, what will its coordinates be at the end of the next 4.95 s interval?

    x= ____m
    y= ____m

    2. Relevant equations

    3. The attempt at a solution
    My first thought was to take the x and y's given and find y=mx+b however I'm not sure that it is relevant or even helpful.

  2. jcsd
  3. Jan 15, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    You should consider both directions independently.

    So x and y satisfy
    x = u t + a,
    y = v t + b

    Equivalently, the distance covered in the second 4.95 seconds is the same as that covered in the first interval.
  4. Jan 15, 2010 #3

    I'm not sure I understand what you're saying. What do the variables represent in your equations? I'm sorry if these are silly questions, however I just finished my second day of Physics and am completely new to it (and also very bad at it!).
  5. Jan 15, 2010 #4


    User Avatar

    Staff: Mentor

    CompuChip is showing the equations of motion for a constant velocity. You can break the problem up into the orthogonal velocities in the x and y directions. So his first equation says that x(t) is equal to x(0) = a, plus an offset given by the velocity u multiplied by the time t.

    Does that help?
  6. Jan 15, 2010 #5

    I understand that much, however I don't understand how those equations work with my numbers?
  7. Jan 15, 2010 #6


    User Avatar

    Staff: Mentor

    You are given a delta-t and a delta-x and a delta-y. From those numbers and those equations, you can figure out what those constants are (u, a, v, b). With those constants and the next delta-t, you can figure out what the final positions will be after the second delta-t.
  8. Jan 15, 2010 #7
    Thank you, I appreciate your time!
  9. Jan 15, 2010 #8
    I definitely over analyzed the question. All you do is find the change in x and changed in y and add them to the last x and y coordinates. I didn't have to do anything with time or velocity.
  10. Jan 15, 2010 #9
    In this case, yes, but what if the next interval was 6.1 seconds. Profs have bbeen known to do such things, esp physics profs!:smile:

    So knowing the velocities is a necessary skill on the third day.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook