A particle moves along a straight line

MATHEMATICS · Subjective · AP · Calculus AB · Differentiation: Definition and Fundamental Properties · Differentiation: Definition and Fundamental Properties

Problem

A particle moves along a straight line, and its displacement xx varies continuously with time tt. (i) Explain, with reasons, why the slope of the displacement–time graph at a particular instant represents the instantaneous velocity of the particle at that instant. (ii) Starting from the definition of average velocity ΔxΔt\displaystyle \frac{\Delta x}{\Delta t}, show algebraically that the instantaneous velocity v(t)v(t) can be written as v(t)=lim⁡Δt→0ΔxΔt\displaystyle v(t)=\lim_{\Delta t \to 0}\frac{\Delta x}{\Delta t}.

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