ch02-p078 - 78. In this solution, we make use of the...

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78. In this solution, we make use of the notation x ( t ) for the value of x at a particular t . Thus, x ( t ) = 50 t + 10 t 2 with SI units (meters and seconds) understood. (a) The average velocity during the first 3 s is given by v xx t avg m/s. = = +− = () () ( ) 30 5 0 3 1 0 3 0 3 80 2 Δ (b) The instantaneous velocity at time t is given by v = dx / dt = 50 + 20 t , in SI units. At t = 3.0 s, v = 50 + (20)(3.0) = 110 m/s. (c) The instantaneous acceleration at time t is given by a = dv / dt = 20 m/s 2 . It is constant, so the acceleration at any time is 20 m/s
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