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Homework Help: Net force from momentum?

  1. Nov 8, 2012 #1


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    1. The problem statement, all variables and given/known data

    An objects momentum is given by the following equation p(t) = 4t3-6t+1. What net force is acting on the objects at t=2?

    2. Relevant equations


    3. The attempt at a solution

    So, I was thinking if F=m*a I can change a and get F=m*(Δv/Δt) and knowing what I know about p, I change it to F=Δp/Δt

    So then I was just solving the equation for t=2 and t=0 to get (21-1)/(2-0) = 10

    Is that correct or am I totally thinking about this wrong?
  2. jcsd
  3. Nov 8, 2012 #2
    Remember that, F=dP/dt
  4. Nov 8, 2012 #3


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    Homework Helper

    Hi Nny! :smile:
    as ben says, F = dp/dt, not ∆p/∆t,

    so your basic idea is right, but your calculation is wrong

    (btw, the proper version of good ol' Newton's second law is not F = ma, it's F = d(mv)dt … force = rate of change of momentum :wink:)
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