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!

Problem is bothering me

  1. Feb 8, 2007 #1
    This should be a really easy problem but for some reason I keep getting the wrong answers.

    The position of an electron is given by = 3.56t - 8.10t2 + 2.53, with t in seconds and in meters. At t = 1.22 s, what are (a) the x-component, (b) the y-component, (c) the magnitude, and (d) the angle relative to the positive direction of the x axis, of the electron's velocity ?

    a) I got the answer to be 3.56 m/s
    b) I thought was -8.10 m/s^2 but for some reason it is wrong or atleast this online homework is telling me it is
    c) I used the magnitude function to find it for the time being 1.22s
    sqrt(4.34^2 + (12.056)^2 + (2.53)^2) and I get 13.06m but it also tells me I am wrong with that.
    d) then I can't find this out because I have the magnitude wrong. But if I did have it right I would have it to be arcCos(3.56/magnitude) right?

    any help would be great thanks :)
  2. jcsd
  3. Feb 8, 2007 #2
    figured out part b and c as I got to the end of the problem I saw they wanted it in velocity so I had to take the derivative of r and then solve for x and y values.

    I am still having trouble with d though...
  4. Feb 8, 2007 #3
    I figured it out it ended up being a negative value because my y-component is negative which would make the magnitude of the vectors in the negative direction, and that gives me -79.79.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?