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Forces - Homework

  1. Mar 6, 2012 #1
    1. The problem statement, all variables and given/known data
    We have a body with mass=1kg and it's on rest. When a force of 5N acts on it , the body displaces 4m. Assume no friction
    Find:
    a)The work that force did
    b)Velocity at the end of the distance(displace)
    a)
    ##Work=Force * Displacement = 5N*4m = 20J##
    ##A=Fd=(5N)(4m)=20J##
    b)
    Uhm,
    ##F=\frac{mv}{t}##, i have no time given. My teacher said this has a solution, it's not wrong. I'm stuck here




    3. The attempt at a solution
    a)
    ##Work=Force * Displacement = 5N*4m = 20J##
    ##A=Fd=(5N)(4m)=20J##
    b)
    Uhm,
    ##F=\frac{mv}{t}##, i have no time given. My teacher said this has a solution, it's not wrong. I'm stuck here
     
  2. jcsd
  3. Mar 6, 2012 #2

    gneill

    User Avatar

    Staff: Mentor

    Look for a kinematic formula that relates velocity, acceleration, and distance, since those are the things you have to work with.
     
  4. Mar 6, 2012 #3
    Ehm, maybe that would be:
    ##a=F/m##
    ##a=5N/1kg=5m/s^2##
    ##a=\frac{Δ v}{Δ t}##
    ##5m/s^2=\frac{v_1-0}{t}##
    I have no v_1(which i have to find) and I have no time..
    If so, would that be
    ##v^2=v_0^2+2ax## which gives us
    ##v^2=0m^2/s^2+2(5m/s^2)(4m)##
    ##v^2=40m^2/s^2##
    ##v=\sqrt{40}=6.324555320336759m/s##
     
  5. Mar 6, 2012 #4

    gneill

    User Avatar

    Staff: Mentor

    That works!
     
  6. Mar 6, 2012 #5
    thanks!
     
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