Question

What is the speed of an object that travels from `( -9,0,1)` to `( -1,4,3 )` over `2 s`?

Answer 1

speed: `sqrt(21) "units"/"sec" ~~4.58 "units"/"sec"`

Explanation:

Distance between `(-9,0,1)` and `(-1,4,3)`
is
`color(white)("XXX")d=sqrt((-1-(-9))^2+(4-0)^2+(3-1)^2)`
`color(white)("XXXx")=sqrt(8^2+4^2+2^2)`
`color(white)("XXXx")=sqrt(64+16+4)`
`color(white)("XXXx")=sqrt(84)`
`color(white)("XXXx")=2sqrt(21)` (units)

Assuming a constant speed, `s`
`color(white)("XXX")"speed" = "distance"/"time"`
So
`color(white)("XXX")s=(2sqrt(21) " units")/(2 " sec")`

`color(white)("XXX")=sqrt(21) "units"/"sec"`

`color(white)("XXX")sqrt(21)~~4.58` (using a calculator)