An object travels North at #9 m/s# for #4 s# and then travels South at #3 m/s# for # 1 s#. What are the object's average speed and velocity?

1 Answer
May 9, 2018

Answer:

#"average speed" = 7.8 m/s# and #"average velocity" = 6.6 m/s#

Explanation:

While going North, the object goes #9 m/cancel(s) * 4 cancel(s) =36 m#.

While going South, the object goes #3 m/cancel(s) * 1 cancel(s) =3 m#.

For average speed , direction does not matter, just total distance and total time.

#"average speed" = "total distance"/"total time" = (36 m+3 m)/(4 s + 1 s) = 7.8 m/s#

For average velocity, direction does matter, so we need the resultant of all displacements (which are vectors) and total time.

#"average velocity" = "net displacement"/"total time" = (36 m-3 m)/(4 s + 1 s) = 6.6 m/s# to the North.

I hope this helps,
Steve