Definitions of Position and Velocity null
If we start knowing the position vs. time x(t), then the velocity, v(t), is the derivative of its position, and the derivative in turn of this velocity is the particle's acceleration, a(t). The force is the particle's mass times a(t).
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\begin
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[ v = \frac
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][ a = \frac
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= \frac{d^
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x}{dt^{2}}]\end
In fact, as you can see, the velocity and acceleration are defined as derivatives of the position, a fact acknowledged by the phrase "the calculus of motion". Newton had to invent calculus of one variable to deal with motion!