An object travels North at 6 m/s for 8 s and then travels South at 2 m/s for 5 s. What are the object's average speed and velocity?

1 Answer
Scott F.
Mar 23, 2017

s_(av)=4.5"m/s"
vec(v_(av))=2.9"m/s North"

Explanation:

The object travels 6"m/s"*8"s"=48"m" north and 2"m/s"*5"s"=10"m" south in a total time of 8"s"+5"s"=13"s"

Average speed refers to total distance over time, regardless of direction. Since the object covers a total distance of 48"m"+10"m"=58"m" in 13"s", its average speed is d/(Deltat)=(58"m")/(13"s")~~4.5"m/s"

Average velocity is a bit more complicated because direction matters; average velocity refers to displacement over time. Let's assign positive to be north for this problem. Since the object has a total displacement of ("+"48"m")+("-"10"m")=48"m"-10"m"="+"38"m" in the same 13"s", its average velocity is (Deltavecx)/(Deltat)=("+"38"m")/(13"s")~~"+"2.9"m/s", so 2.9"m/s North"

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