Question

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

Answer 1

The average speed is 6m/s; the average velocity is 0.75 m/s North.

Explanation:

First, we must determine the displacement of the object during each time interval.

During the first 9s

`d=vxxt = 6m/sxx9s = 54m` North

During the next 7s

`d=vxxt = 6m/sxx7s = 42m` South

For the average speed , we consider only the total distance travelled and the total time taken

`v_"ave" = d-:t = 96 m-:16 s = 6 m/s`

For the average velocity , we consider the net displacement and the time taken. The net displacement has been only 12 m North.

`vecv_"ave"=vecd -:t = 12m N -: 16s = 0.75 m/s` North