An object travels North at 8 m/s for 4 s and then travels South at 6 m/s for 7 s. What are the object's average speed and velocity?

1 Answer
Aug 28, 2017

Average speed: 6 8/11 m/s

Average velocity: 10/11 m/s " South"

Explanation:

{: (,ul("Distance"),color(white)("xxx"),ul("Displacement")), ("first 4 seconds",8m/sxx4s=32m,,8m/s N xx4s =32 m N), ("second 7 seconds",6m/sxx7s=42m,,6m/s Sxx7s=42 m S) :}
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Total time: 4 s + 7 s=11s

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Total distance: =32 m + 42 m = 74m

Average speed: "distance"/"time"=(74 m)/(11 s)=6 8/11 m/s

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Total displacement: 32 m color(red)N +42 m S
color(white)("XXXXXXXXXXXXXXXXXX")=color(red)-32m color(red)S +42 m S
color(white)("XXXXXXXXXXXXXXXXXX")=10 m S

Average velocity: "displacement"/"time"= (10 mS)/(11s)=10/11 m/s S