# An object travels North at 8 m/s for 2 s and then travels South at 3 m/s for 4 s. What are the object's average speed and velocity?

Mar 14, 2018

Average speed = 4.67 m/s
Average velocity = 0.67 m/s N

#### Explanation:

Speed, a scalar measurement, is how fast an object moves over a surface; velocity, a vector quantity, is how fast and in what direction.

Speed
= $8 \frac{m}{s} + 8 \frac{m}{s} + 3 \frac{m}{s} + 3 \frac{m}{s} + 3 \frac{m}{s} + 3 \frac{m}{s} = 28 \frac{m}{s}$ over 6s

Average speed = $\frac{28}{6} = 4.667 \frac{m}{s}$

Velocity is how far an object is displaced from its starting point over a period of time.

The object moved 8m/s North x 2s = 16 m North, then 3m/s South x 4s = 12 m South, for a total displacement of 4 m North over 6 seconds.

Average velocity $= \frac{\left(4 m\right) N}{6 s} = 0.67 \frac{m}{s} N$