Question

What is the speed of an object that travels from `( -4,6,2)` to `( -3, 9,-6 )` over `3 s`?

Answer 1

The displacement from one point to the other is `d=sqrt((x_2-x_1)^2+(y_2-y_1)^2+(z_2-z_1)^2)=sqrt((-3-(-9))^2+(9-6)^2+(-6-2)^2)`
`=sqrt(36+9+64)=sqrt(109)~~10.44` units.

Speed = distance/time = `10.44/3=3.5` `ms^-1`.