An object travels North at $8 m s^{- 1}$ $8 ms^-1$ for $7 s$ $7 s$ and then travels South at $7 m s^{- 1}$ $7 ms^-1$ for $3 s$ $3 s$ . What are the object's average speed and velocity?

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Answer 1 · 2016-04-24T21:55:52

Average speed:

$s p e e d = \frac{distance}{t i m e} = \frac{56}{10} = 5.6$ $speed=("distance")/(time)=56/10=5.6$ $m s^{- 1}$ $ms^-1$

Average velocity:

$v e l o c i t y = \frac{displacement}{t i m e} = \frac{21}{10} = 2.1$ $velocity=("displacement")/(time)=21/10=2.1$ $m s^{- 1}$ $ms^-1$

In brief, the average speed relates to the distance traveled, the average velocity to the displacement.

Distance traveled North: $d = v t = 8 \cdot 7 = 56$ $d=vt=8*7=56$ $m$ $m$
Distance traveled South: $d = v t = 7 \cdot 3 = 21$ $d=vt=7*3=21$ $m$ $m$

Total distance traveled: $77$ $77$ $m$ $m$
Displacement: $35$ $35$ $m$ $m$

Total time taken: $10$ $10$ $s$ $s$

Average speed:

$s p e e d = \frac{distance}{t i m e} = \frac{56}{10} = 5.6$ $speed=("distance")/(time)=56/10=5.6$ $m s^{- 1}$ $ms^-1$

Average velocity:

$v e l o c i t y = \frac{displacement}{t i m e} = \frac{21}{10} = 2.1$ $velocity=("displacement")/(time)=21/10=2.1$ $m s^{- 1}$ $ms^-1$

An object travels North at 8ms−18 ms^-1 for 7s7 s and then travels South at 7ms−17 ms^-1 for 3s3 s. What are the object's average speed and velocity?