Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Tangential and radial particle acceleration

  1. Feb 28, 2007 #1
    1. The problem statement, all variables and given/known data
    A particle moves in the xy plane in a circle centered origin. At a certain instant the velocity and acceleration of the particle are 4.6j m/s and (2.3i - 2.1j) m/s^2. What are the x and y coordinates of the particle at this moment


    2. Relevant equations
    ar=-v^2/r


    3. The attempt at a solution
    I took the magnitude of the radial acceleration and got 3.11 m/s^2 and plugged it into the equation. I got -6.8 for my radius and was told that was the wrong answer for the x coordinate. Then I tried plugging in 2.3 for the radial acceleration and got -9.2 for my radius. Does the -2.1j m/s^2 not play a factor in this problem? I got x=-9.2, but I don't know how to solve for the y component of the problem.
     
  2. jcsd
  3. Feb 28, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    How did you get this? Are you assuming that the particle is moving with a constant speed? (You are given the total acceleration, not the radial acceleration.)
    The velocity should tell you the y-coordinate, since it moves in a circle.
     
  4. Feb 28, 2007 #3

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The velocity is given as being in the 'j' direction only. That should give you a hint on the possible location of the y coordinate. Your value of the centripetal acceleration that you must use depends on the value of the y coordinate you must find first.
     
  5. Feb 28, 2007 #4
    The y coordinate equal 0?
     
  6. Feb 28, 2007 #5

    Doc Al

    User Avatar

    Staff: Mentor

    Absolutely. That's the only way to make sense of the given velocity, since that velocity must be tangential to the circle at all times.
     
  7. Feb 28, 2007 #6
    Thanks, I appreciate the help.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook