An object travels North at 1 m/s for 8 s and then travels South at 6 m/s for 4 s. What are the object's average speed and velocity?

1 Answer
Alan P.
Apr 8, 2017

Average speed: 2 2/3 m/scolor(white)("XXX")Average velocity: 1 1/3 m/s ["South"]

Explanation:

The object travels:
color(white)("XXX")North: 1 m/s xx 8 s =8 m
color(white)("XXX")South: 6 m/s xx 4 s =24 m

For a total distance of 32 m
and
color(white)("XXX")(noting that 24 m" South" = -24 m" North")
a resulting displacement of 8 m (N) - 24 m (N)=-16 m (N)

Total travel time: 8 s + 4 s = 12 s

Average speed = ("total distance")/("total time")= (32 m)/(12 s)=2.66bar6 m/s

Average velocity=("resulting displacement")/("total time")=(-16 m "(N)")/(12 s)=-1.33bar3 m/s "(N)"

color(white)("XXX")orcolor(white)("XXXXXXXXXXXXXXXXXXXXXX")+1.33bar3 m/s "(S)"

Notice that displacement and velocity should always contain a component indicating direction.

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