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Vector components problem determinings final kinetic energy

  1. Nov 21, 2009 #1
    1. The problem statement, all variables and given/known data

    question 2

    http://web.viu.ca/hearnd/Courses/Phys121/F02Test2/Page%201.htm" [Broken]
    3. The attempt at a solution


    I have been trying to do question 2 on the practice test but I am stuck.
    I was trying to calculate the final velocities along each vector by using the equation
    vxf^2=vxi^2+2aX
    first i determined the acceleration by dividing each of the force vectors by the mass of the object
    but since one of the accelerations was negative I could not calculate the final velocity of that vector

    so now I am trying with the total vectors for

    sqrt(4^2 +0 +0)

    because only one component out of three has any initial velocity

    so vi=4m/s

    F=sqrt(4^2+(-3)^2+2^2)=5.385N
    so
    a= 2.69258 m/s

    d=sqrt(16^2+4^2+8^2)= 18.3303

    v=sqrt(4+2(2.69258)(18.3303))
    vf=10.13

    Ek=106.09

    which is wrong

    any help would be appreciated
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 21, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Work done = F.r = Change in KE.
     
  4. Nov 21, 2009 #3
    Thanks
     
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