# An object travels North at  8 m/s for 8 s and then travels South at  3 m/s for  7 s. What are the object's average speed and velocity?

Nov 25, 2017

Average speed = 5.7 m/s

Average velocity = 2.9 m/s

#### Explanation:

Distance along north$= \text{8 m"/cancel"s" × 8 cancel"s" = "64 m}$

Distance along south$= \text{3 m"/cancel"s" × 7 cancel"s" = "21 m}$

Total distance$= \text{64 m + 21 m" = "85 m}$

Displacement$= \text{64 m North" - "21 m South" = "43 m North}$

Average speed$= \text{Total distance"/"Time" = "85 m"/"8 s + 7 s" = "5.7 m/s}$

Average velocity$= \text{Displacement"/"Time" = "43 m"/"8 s + 7 s" = "2.9 m/s}$