An object travels North at #7 m/s# for #3 s# and then travels South at #9 m/s# for # 2 s#. What are the object's average speed and velocity?

1 Answer
May 4, 2016

Answer:

Average speed #=7.8 m/s#

Average velocity #=0.6 m/s " North"#

Explanation:

Total distance traveled:
#color(white)("XXX")7 m/sxx3 s + 9 m/sxx2 s = 21 m + 18 m = 39 m#
Total time:
#color(white)("XXX")3 s + 2 s = 5 s#
Average speed:
#color(white)("XXX")(39 m)/(5 s) =7.8 m/s#

Displacement:
#color(white)("XXX")7 m/s xx 3 s " North" +9 m/s xx 2 s " South"#
#color(white)("XXX")=21 m " North" +18 m " South"#
#color(white)("XXX")=3 m " North"#
Total time:
#color(white)("XXX")3 s + 2 s = 5 s#
Average velocity:
#color(white)("XXX")(3 m " North")/(5 s) = 0.6 m/s " North"#