An object travels North at $8$ $ms^-1$ for $9$ $s$ and then travels South at $5$ $ms^-1$ for $3$ $s$ . What are the object's average speed and velocity?

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Answer 1 · 2017-07-10T07:06:16

Average speed = $("total distance traveled")/("total time taken")=93/12=7.75$ $ms^-1$

Average velocity = $("total displacement")/("total time taken")=63/12=5.25$ $ms^-1$ $N$

Distance traveled North:

$s_N=ut=8xx9=72$ $m$

Distance traveled South:

$s_S = ut = 5xx3=15$ $m$

Total distance traveled:

$s=s_N+s_S=78+15=93$ $m$

Total time:

$t=9+3=12$ $s$

Average speed = $("total distance traveled")/("total time taken")=93/12=7.75$ $ms^-1$

If we take North as the positive direction, total displacement:

$s=s_N-s_S=78-15=63$ $m$ $N$

This is the distance of the object from its starting point, and includes a direction.

Average velocity = $("total displacement")/("total time taken")=63/12=5.25$ $ms^-1$ $N$

An object travels North at 88 ms^-1ms^-1 for 99 ss and then travels South at 55 ms^-1ms^-1 for 33 ss. What are the object's average speed and velocity?