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!

Homework Help: Applications of vector algebra to physics

  1. Jul 29, 2009 #1
    1. The problem statement, all variables and given/known data

    A ball of mass 1 kg is acted upon by three forces:
    Fl = (2i + 4j - 3k) N, F2 = (-3i - j + 2k) Nand F3 = (i - 5j - k) N.
    Determine a vector expression for the acceleration of the particle.
    If, at time t = 0, it has position r = (i +j) m and velocity u = (i +3j)m/s, write
    down the position vector of the ball at time t. Hence, determine its position and
    velocity after 2 seconds.

    2. Relevant equations

    3. The attempt at a solution

    resultant force & acceleration due to forces:

    Fresultant = F1+F2+F3 = -(2j+2k)N

    F=ma, m=1kg, therefore a = -(2j+2k)ms-2

    position vector at (t), and velocity and position at t=2:


    therefore r(t)=(i+j)+(i+3j)-[tex]\frac{1}{2}[/tex](j+k)t2

    so at t=2,

    r(2)=(3i+5j-2k), and v(2)=(i+j-2k)ms-1

    any problems? thanks for all the help always!
  2. jcsd
  3. Jul 29, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    No conceptual problems. You are being pretty sloppy about putting the numbers into r(t)=r(0)+v(0)*t+(1/2)*a*t^2, though. I'd try that part again.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook