An object travels North at 6 m/s for 5 s and then travels South at 7 m/s for 5 s. What are the object's average speed and velocity?

1 Answer
Jan 14, 2018

Average speed =6.5m/s
Average velocity = -0.5m/s

Explanation:

Average "velocity" = "displacement"/"time elapsed"
bar v = (Deltax)/(Delta t)
Average "speed" = "distance traveled"/"time elapsed"
bar s = d/(Delta t)

Going north at 6m/s for 5s is 30m, and going south at 7m/s for 5s is 35m, hence the object in 10s has effectively gone south for 5m as a displacement despite it has actually traveled a total distance of 65m.

Bear in mind that for displacement going north is positive, south negative:

Delta x = 6m/s*5s - 7m/s*5s= 30m-35m= - 5m

d = 30m + 35m = 65 m

Delta t = 5s+5s = 10s

bar v = (Deltax)/(Delta t) =-(5m)/(10s) = -0.5m/s
bar s=d/(Delta t)=(65m)/(10s) = 6.5 m/s