# What is the speed of an object that travels from ( -2,1,2)  to ( -3, 0,-7 )  over 3 s?

Jan 17, 2016

#### Answer:

The speed of the object $= \text{distance"/"time"=3.037 " units/s}$

#### Explanation:

• If you take the two points as standard form vectors, the distance between them would be the magnitude of the vector of their difference.

So take $\vec{A} = < - 2 , 1 , 2 > , \vec{B} = < - 3 , 0 , - 7 >$

• $\vec{A - B} = < - 1 , 1 , 9 >$
$| A - B | = \sqrt{- {1}^{2} + {1}^{2} + {9}^{2}}$
$| A - B | = \sqrt{83} = 9.110$
$\text{distance} = 9.110$

• The speed of the object $= \text{distance"/"time}$
$= \frac{9.110}{3} = 3.037 \text{ units/s}$