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?

1 Answer
May 14, 2017

Answer:

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