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Homework Help: Resulting force after two objects collide

  1. Jan 24, 2016 #1
    1. The problem statement, all variables and given/known data
    The car A has a weight of 4000 lb and is traveling to the right at 3 ft/s. Meanwhile a 2000 lb car B is traveling at 6 ft/s to the left. If the cars crash head-on, and at a time instant during the crash the impact force on A is 900 lb to the left, what is the magnitude and direction of the impact force exerted on B at the instant?

    So essentially,

    Car A (4000 lb; v= 3 ft/s) → ← Car B (2000 lb; v = 6 ft/s)

    A) 900 lb to the left
    B) 450 lb to the left
    C) 450 lb to the right
    D) 1800 lb to the left
    E) 900 lb to the right

    2. Relevant equations
    F1=F2 ?

    3. The attempt at a solution
    This is a question in my Statics hw and we have only been learning about forces and haven't concerned ourselves with the role that v has to play. This seems like something I learned in my first class of Newtonian physics a long time ago that I can't recall.

    From a theoretical standpoint, I might assume that due to Newton's third law, everything has an equal and opposite reaction, that Car A would exert the same amount of force on B: the force on car B would be 900 lb to the right.

    But then, I imagine that because Car B has a greater velocity, A would have less of an impact on it.

    So I assume the answer is either C or E.
    Is there an equation I can use to account for velocity and Force? I tried googling it and couldn't find anything.
  2. jcsd
  3. Jan 24, 2016 #2
    Newton's third law.
  4. Jan 24, 2016 #3

    Suraj M

    User Avatar
    Gold Member

    I feel you should go by newtons 3rd law itself.
  5. Jan 24, 2016 #4
    I went with Newton's third law and got it right! Thanks!
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