Question

An object travels North at `6 m/s` for `5 s` and then travels South at `7 m/s` for `5 s`. What are the object's average speed and velocity?

Answer 1

Average speed `=6.5m/s`
Average velocity`= -0.5m/s`

Explanation:

Average `"velocity" = "displacement"/"time elapsed"`
`bar v = (Deltax)/(Delta t)`
Average `"speed" = "distance traveled"/"time elapsed"`
`bar s = d/(Delta t)`

Going north at 6m/s for 5s is 30m, and going south at 7m/s for 5s is 35m, hence the object in 10s has effectively gone south for 5m as a displacement despite it has actually traveled a total distance of 65m.

Bear in mind that for displacement going north is positive, south negative:

`Delta x = 6m/s*5s - 7m/s*5s= 30m-35m= - 5m`

`d = 30m + 35m = 65 m`

`Delta t = 5s+5s = 10s`

`bar v = (Deltax)/(Delta t) =-(5m)/(10s) = -0.5m/s`
`bar s=d/(Delta t)=(65m)/(10s) = 6.5 m/s`