An object travels North at # 8 m/s# for #8 s# and then travels South at # 5 m/s# for # 2 s#. What are the object's average speed and velocity?
1 Answer
Explanation:
We're asked to find both the average speed and the average velocity of the object with given displacements.
Let's calculate the average velocity first.
The average velocity of an object is defined by the equation
But since this object is moving only northward and southward, which we'll say is along the
where

#v_"avy"# is the average#y# velocity 
#Deltay# is the change in#y# position of the object 
#Deltat# is the total change in time, which is#8# #"s"# #+ 2# #"s"# #= color(blue)(10# #color(blue)("s"#
For reference, we'll call north the positive
1:
2:
The total change in
And so the average velocity is
Now we'll find the average speed of the object.
The average speed of an object is defined as
The total distance traveled is merely the sum of the distances traveled disregarding the signs and directions, so the total distance is
And the average speed is thus