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Homework Help: Force in kinetic energy/force in momentum =1

  1. Apr 24, 2010 #1

    morrobay

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    Gold Member

    1. The problem statement, all variables and given/known data
    mass=20
    V1=0
    V2=10ft/sec
    t=2 sec
    a=5'/sec/sec
    x=10ft
    I want to show that the force in momentum and in kinetic energy from above data is the same. With the understanding that simple algebra is being superimposed on calculus.


    2. Relevant equations
    K.E.= integral of force over distance= max=mdv/dt (dx) =1/2mv^2
    momentum = integral of force over time = mv
    force= K.E./change in distance
    force=momentum/change in time



    3. The attempt at a solution
    K.E.= 1000 lb (ft/sec)^2
    momentum=200 lb(ft/sec)
    The force from kinetic energy = 1000 lb (ft/sec)^2 /10ft =100 lb
    The force from momentum = 200 lb (ft/sec)/2 sec= 100 lb
    Same force, correct ?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Apr 25, 2010
  2. jcsd
  3. Apr 24, 2010 #2

    rock.freak667

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    Homework Helper

    I am not sure how your units work, but lbs is a force, so you'd need to divide by acceleration due to gravity to get the mass.
     
  4. Apr 25, 2010 #3

    morrobay

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    Gold Member

    OK the mass =20 by correction.
    Now is the 100 lb force correct ?
     
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