An object travels North at # 2 m/s# for #6 s# and then travels South at # 7 m/s# for # 4 s#. What are the object's average speed and velocity?

Question

An object travels North at #  2  m/s# for #6 s# and then travels South at #  7   m/s# for # 4    s#.  What are the object's average speed and velocity?

Charles Aeschliman · Accepted Answer

Clearly,distance covered by the object in total #10 s# is #6*2 + 7*4=40 m#

Hence, average speed is calculated as follows: total distance traveled / total time spent = 40/10 = 4 m/s.

Again, net displacement is #(6*2 - 7*4)=-16 m#

So,average velocity = net displacement/total time taken = #-16/10=-1.6 ms^-1#

A negative sign means that the average velocity is moving southward.

Nora Arzate · Answer

undefined Average speed = total distance / total time
Total distance = (distance traveled north) + (distance traveled south)
Distance traveled north = (speed north) * (time north)
Distance traveled south = (speed south) * (time south)

Average velocity = displacement / total time
Displacement = final position - initial position
Final position = (position north) - (position south)
Initial position = 0 (since the object starts at the same point)

Average speed = (2 * 6 + 7 * 4) / (6 + 4) = 44 / 10 = 4.4 m/s
Displacement = (2 * 6) - (7 * 4) = 12 - 28 = -16 m
Average velocity = (-16) / (6 + 4) = -1.6 m/s