Nathanial Frost

2023-02-24

The position of a particle moving along x-axis is given by $x=\left(5{t}^{2}-4t+20\right)m$, where t is in second. Find the magnitude average velocity between 1 s and 3 s.
A)10 m/.s
B)16 m/.s
C)14 m/.s
D)5 m/.s

### Answer & Explanation

Haylie Long

The right option is B 16 m/.s
We know, $x=\left(5{t}^{2}-4t+20\right)m$
t=1 s; ${x}_{in}=5×\left(1{\right)}^{2}-4×\left(1\right)+20=21m$
$t=3s;{x}_{in}=5×\left(3{\right)}^{2}-4×\left(3\right)+20=53m$
${v}_{avrg}=\mathrm{△}x\mathrm{△}t$
${v}_{avrg}=\left(53-21\right)/\left(3-1\right)=16m/s$

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