An object travels North at #7 m/s# for #3 s# and then travels South at #9 m/s# for # 4 s#. What are the object's average speed and velocity?

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Answer 1 · 2017-01-29T17:16:42

Average speed is #8 1/7# #m/s# and average velocity is #2 1/7# #m/s# south.

As the object travels North at #7# #m/s# for #3# #s#,

the displacement is #7xx3=21# #m# north

then the object travels South at #9# #m/s# for #4# #s#,

the displacement is #9xx4=36# #m# south

Hence, net displacement is #36-21=15# #m# south in #3+4=7# #s#

As total distance covered is #21+36=57# #m# in #7# seconds,

average speed is #57/7=8 1/7# #m/s#

But average velocity is #15/7=2 1/7# #m/s# south.