# An object travels North at 9 m/s for 7 s and then travels South at 7 m/s for  6 s. What are the object's average speed and velocity?

Feb 12, 2017

The average speed is the total distance over the total time.

The total distance i s$63 + 42 = 105$ meters

The total time is $7 + 6$ seconds $= 13$ seconds

Thus, the average speed is $\frac{105}{13} m {s}^{-} 1$ or 8.08 m/s

The average velocity is the total displacement over the total time.

If the object goes $63$m North and then comes back $42$ meters South, then it is $21$m North of its starting point.

The total time is the same $= 13$ seconds.

Thus, the average velocity is $\frac{21}{13} m {s}^{-} 1$ North.

Don't forget to add the direction "North" because velocity is a vector quantity.