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

1 Answer
Feb 27, 2017

Answer:

#Sav = 3.5 m/s#; #Vav = 1 m/s# South

Explanation:

Travel distance north is #5 m/s xx 1 s = 5m# (shorter)

Travel distance south is #3 m/s xx 3s = 9m# (longer)

Average speed is the total distance travelled divided by total time.

#Sav = (5m + 9m)/(1s + 3s) = (14m)/(4s) = 3.5 m/s#

Average velocity is the resultant change in velocity divided by the total time where the final velocity is South;

#Vav = -Vn + Vs#

Note that #Vn# is negative because its direction is opposite to the final velocity.

#Vav = (-5mn + 9ms)/(1s + 3s) = (4m)/(4s) = 1m/s South#

This scenario may occur in real life when a ping pong ball is returned from a serve.