An object travels North at # 4# # ms^-1# for #3# #s# and then travels South at # 6 # #ms^-1# for # 8# # s#. What are the object's average speed and velocity?

1 Answer
David G.
Apr 28, 2016

The average speed is the total distance over the time, the average velocity is the total displacement over time. Speed = #5.45# #ms^-1#, velocity = #3.27# #ms^-1#.

Explanation:

Find the distances traveled in each step:

#d=vt=4*3=12 #m# N

#d=vt=6*8=48 #m# S

The total distance is the simple sum of these two distances, #60# #m#.

The total displacement is the difference between them, #36# #m# S

The total time is #8+3=11# #s#

To find the average speed:

#speed=("distance")/("time")=60/11~~5.45# #ms^-1#

To find the average velocity:

#velocity=("distance")/("time")=36/11~~3.27# #ms^-1#

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