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

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Answer 1 · 2017-01-29T17:16:42

Average speed is $8 1/7$ $m/s$ and average velocity is $2 1/7$ $m/s$ south.

As the object travels North at $7$ $m/s$ for $3$ $s$ ,

the displacement is $7xx3=21$ $m$ north

then the object travels South at $9$ $m/s$ for $4$ $s$ ,

the displacement is $9xx4=36$ $m$ south

Hence, net displacement is $36-21=15$ $m$ south in $3+4=7$ $s$

As total distance covered is $21+36=57$ $m$ in $7$ seconds,

average speed is $57/7=8 1/7$ $m/s$

But average velocity is $15/7=2 1/7$ $m/s$ south.

An object travels North at 7 m/s7 m/s for 3 s3 s and then travels South at 9 m/s9 m/s for 4 s 4 s. What are the object's average speed and velocity?