# An object travels North at  12 m/s for 1 s and then travels South at  5 m/s for  7 s. What are the object's average speed and velocity?

Apr 25, 2016

Average speed $5 \frac{7}{8} \frac{m}{s}$
Average velocity $2 \frac{7}{8} \frac{m}{s} \text{South}$

#### Explanation:

Distance traveled $= 12 \frac{m}{s} \times 1 s + 5 \frac{m}{s} \times 7 s = 47 m$
Total time$= 1 s + 7 s = 8 s$
Average speed$= \frac{47 m}{8 s} = 5 \frac{7}{8} \frac{m}{s}$

Displacement $= 12 m \text{North" + 35 m "South" = -12 m "South" +35 m "South" = 23 m "South}$
Average velocity $= \frac{23 m}{8 s} = 2 \frac{7}{8} \frac{m}{s} \text{South}$