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
Mar 23, 2017

Answer:

#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"#