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

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Answer 1 · 2018-03-13T18:46:27

Average speed $"= 4.23 m/s"$

Average velocity $"= 0.077 m/s along South"$

$"Average speed" = "Total distance"/"Total time"$

$<< V >> = (v_1t_1 + v_2t_2)/(t_1 + t_2)$

$<< V >> = (("3 m/s × 9 s") + ("7 m/s × 4 s"))/("9 s + 4 s") = color(blue)"4.23 m/s"$

$"Average velocity" = "Total displacement"/"Total time"$

$<< vecV >> = (vec(v_1)t_1 + vec(v_2)t_2)/(t_1 + t_2)$

$<< vecV >> = (("3 m/s" (hatj) × "9 s") + ("7 m/s" (-hatj) × "4 s"))/("9 s + 4 s")$

$<< vecV >> = (27hatj - 28hatj)/13\ "m/s"$

$<< vecV >> = (-1 hatj)/13\ "m/s" = -0.077hatj\ "m/s" = color(blue)"0.077 m/s along South"$

An object travels North at 3 m/s 3 m/s for 9 s9 s and then travels South at 7 m/s 7 m/s for 4 s 4 s. What are the object's average speed and velocity?