An object travels North at 5 m/s for 8 s and then travels South at 5 m/s for  2 s. What are the object's average speed and velocity?

Apr 28, 2018

Speed is distance traveled per unit time, whereas velocity is displacement per unit time.

Recall,

$\nu = \frac{\Delta x}{t} \text{ } \overline{s} = \frac{d}{t}$

We will assume an x-y coordinate system to be the reference frame, where south is negative and north is positive in direction.

Let's derive the magnitude of the displacement in each direction given your data,

$\Delta {x}_{\text{N" = (5"m")/"s" * 8.0"s" approx 40"m}}$
$\Delta {x}_{\text{S" = (5"m")/"s" * 2.0"s" approx 10"m}}$

$\Sigma d = 50 \text{m}$, and
$\Sigma t = 10 \text{s}$

Hence,

bars = (50"m")/(10"s") = (5"m")/"s", and

nu = (40"m" - 10"m")/(10"s") = (3"m")/"s"

are the average speed and velocities of the moving body.