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Force problem

  1. Sep 7, 2004 #1
    A cart of mass 20kg, initially at rest, is pushed with a net force of 40N on a flat surface. If the cart is pushed 5m, what is the final KE? What is the final velocity? (Assume no heat loss)



    Basically I understand to use: W = F x d to find out the work done, but where does the mass of the cart come into play?

    Also, if the cart only goes 5m, how can I find the velocity?
     
  2. jcsd
  3. Sep 7, 2004 #2
    You don't need to use mass for the first part, but for the second. You divide the force by the mass to get its acceleration and then you use one of the thee kinematic equations to find v final using the distance travelled and the acceleration.
     
  4. Sep 7, 2004 #3
    Ok, so the accel is 2 m/s^2

    Which kinematic equation will solve for velocity now that I know the mass, accel, but not time?
     
  5. Sep 7, 2004 #4
    You know work = change in kinetic energy (q1)
    If you already have kinetic energy, you can solve q2 :
    KE = function of speed and mass
    Invert this to find the speed.
     
  6. Sep 7, 2004 #5
    Use

    Kinetic Energy Gained = Work done
    (assuming no heat losses)
    1/2 mv^{2} = F.s
    therefore v = sqr.rt { 2F.s/m}.
     
  7. Sep 7, 2004 #6
    Thanks guys, I completely overlooked that...such an easy problem and I made it harder than it needed. :yuck:
     
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