Question

An object travels North at `6 m/s` for `8 s` and then travels South at `2 m/s` for `5 s`. What are the object's average speed and velocity?

Answer 1

`s_(av)=4.5"m/s"`
`vec(v_(av))=2.9"m/s North"`

Explanation:

The object travels `6"m/s"*8"s"=48"m"` north and `2"m/s"*5"s"=10"m"` south in a total time of `8"s"+5"s"=13"s"`

Average speed refers to total distance over time, regardless of direction. Since the object covers a total distance of `48"m"+10"m"=58"m"` in `13"s"`, its average speed is `d/(Deltat)=(58"m")/(13"s")~~4.5"m/s"`

Average velocity is a bit more complicated because direction matters; average velocity refers to displacement over time. Let's assign positive to be north for this problem. Since the object has a total displacement of `("+"48"m")+("-"10"m")=48"m"-10"m"="+"38"m"` in the same `13"s"`, its average velocity is `(Deltavecx)/(Deltat)=("+"38"m")/(13"s")~~"+"2.9"m/s"`, so `2.9"m/s North"`