An object travels North at 6 m/s6ms for 3 s3s and then travels South at 5 m/s5ms for 7 s7s. What are the object's average speed and velocity?

1 Answer
May 20, 2017

Average speed is 5.3 m/s5.3ms.

Average velocity is 1.7 m/s " South"1.7ms South.

Explanation:

"Average speed" = "Distance"/"Time"Average speed=DistanceTime

The total distance is 6 m/s * 3s + 5m/s * 7s = 18 m + 35 m = 53m6ms3s+5ms7s=18m+35m=53m.

The total time is 3s + 7s = 10s3s+7s=10s.

Therefore the average speed is (53m)/(10s) = 5.3 m/s53m10s=5.3ms.

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"Average velocity" = "Displacement"/"Time"Average velocity=DisplacementTime

The total displacement is :

18m " North" + 35m " South" = 17m " South"18m North+35m South=17m South

The total time is 3s+7s = 10s3s+7s=10s.

Therefore the average velocity is (17m " South")/(10s) = 1.7 m/s " South"17m South10s=1.7ms South

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Note that the average speed has no direction while the average velocity does (South).