Question

An object travels North at `7 m/s` for `3 s` and then travels South at `9 m/s` for `2 s`. What are the object's average speed and velocity?

Answer 1

Average speed `=7.8 m/s`

Average velocity `=0.6 m/s " North"`

Explanation:

Total distance traveled:
`color(white)("XXX")7 m/sxx3 s + 9 m/sxx2 s = 21 m + 18 m = 39 m`
Total time:
`color(white)("XXX")3 s + 2 s = 5 s`
Average speed:
`color(white)("XXX")(39 m)/(5 s) =7.8 m/s`

Displacement:
`color(white)("XXX")7 m/s xx 3 s " North" +9 m/s xx 2 s " South"`
`color(white)("XXX")=21 m " North" +18 m " South"`
`color(white)("XXX")=3 m " North"`
Total time:
`color(white)("XXX")3 s + 2 s = 5 s`
Average velocity:
`color(white)("XXX")(3 m " North")/(5 s) = 0.6 m/s " North"`