# What is the speed of an object that travels from ( 7,-8,1)  to ( -1,4,-6 )  over 2 s?

Mar 1, 2016

$v \cong 8 , 02 \frac{m}{s}$
$\text{1- we must find distance between the point of (7,-8,1)}$$\text{ and (-1,4,-6)}$
$\Delta s = \sqrt{{\left(- 1 - 7\right)}^{2} + {\left(4 + 8\right)}^{2} + {\left(- 6 - 1\right)}^{2}}$
$\Delta s = \sqrt{64 + 144 + 49} \text{ "Delta s=sqrt257 " m}$
$\text{2- now, we can calculate speed using : } v = \frac{\Delta s}{\Delta t}$
$v = \frac{\sqrt{257}}{2}$
$v \cong 8 , 02 \frac{m}{s}$