Question

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?

Answer 1

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 `105/13 ms^-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 `21/13ms^-1` North.

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