Question

An object travels North at `4 m/s` for `1 s` and then travels South at `5 m/s` for `3 s`. What are the object's average speed and velocity?

Answer 1

Average Speed: `4.75` m/s
Average Velocity: `-2.75` m/s

Explanation:

To calculate the object's average speed (direction doesn't matter), we use the formula:
`s_(avg)=("total distance")/("change in time")`

We know that the object traveled for 4 m/s for 1 s then traveled 5 m/s for 3 s, therefore:
`4(1)+5(3)=4+15=19` is the total distance traveled in meters
`1+3=4` is the change in time

Therefore,
`s_(avg)=19/4=4.75` m/s

To calculate the object's average velocity (direction matters), we use the formula:
`v_(avg)=("displacement")/("change in time")`

Let North be positive and South be negative. We know that the object traveled +4 m/s for 1 s then traveled -5 m/s for 3 seconds, therefore:
`4(1)-5(3)=4-15=-11` is the total displacement in meters
`1+3=4` is the change in time

Therefore,
`v_(avg)=-11/4=-2.75` m/s