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B I just found a new way to calculate Force

  1. May 10, 2017 #1
    I found a new way to calculate force without getting the acceleration when you have velocity, mass, & time.
    F = (m/t)v
    I just find this more efficient than getting the acceleration, why not use one formula.
  2. jcsd
  3. May 10, 2017 #2


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    Staff: Mentor

    But as acceleration is change of velocity per time, you get ##F=(m/t)v=(mv/t)=m(v/t)=ma##, which is acceleration again.
  4. May 10, 2017 #3


    Staff: Mentor

    So according to your formula, force always decreases as time increases. Is this what you observe?
  5. May 10, 2017 #4
    It seems so, yes
  6. May 10, 2017 #5
    yeah, I just stated that I don't have to go to a=v/t anymore
  7. May 10, 2017 #6


    Staff: Mentor

    No, it doesn't. In fact, as an object falls from a great distance the force increases as time increases, in direct opposition to your formula.

    When you write a formula in physics, it is important to check if it is consistent with experiment. Yours is not.
  8. May 10, 2017 #7
    oh, I see....
    also in my formula, force increases due to it's velocity. The faster the object, the greater the force?
    but the formula does not contend with reality though, I shall take a note on that, thanks
  9. May 10, 2017 #8
    Also your understanding of force only works for constant accelerations.

    constant a and constant m:
    The force equation is F=ma, we could know the change in velocity Δv and the amount of time it took for that change to occur Δt. Then acceleration is a constant a=Δv/Δt. You could them formulate an equation F=(m/Δt)*Δv but this is trivial.

    variable a and m:
    Force eq. is F=dp/dt. this is the rate of change of momentum using differential calculus. You could have a changing m in a rocket, where the acceleration and velocity change as the rocket flies up, but the mass decreases as huge containers of fuel are emptied. Since p=mv, the force equation could read F=d(mv)/dt and your discovery is actually quite meaningful as you have noticed that Forces aren't limited to changes in velocity over time only.
  10. May 10, 2017 #9


    Staff: Mentor

    Yes, good observation. It would mean that objects at rest would get stuck because v=0 so F=0. You could throw a ball up and have it never come down but just rest at the apex forever, and you would never be able to get out of bed in the morning.
  11. May 10, 2017 #10


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    You could have written:

    ##F = m\frac{dv}{dt}##
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