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

Apr 24, 2016

Average speed:

$s p e e d = \frac{\text{distance}}{t i m e} = \frac{56}{10} = 5.6$ $m {s}^{-} 1$

Average velocity:

$v e l o c i t y = \frac{\text{displacement}}{t i m e} = \frac{21}{10} = 2.1$ $m {s}^{-} 1$

#### Explanation:

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

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

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

Total time taken: $10$ $s$

Average speed:

$s p e e d = \frac{\text{distance}}{t i m e} = \frac{56}{10} = 5.6$ $m {s}^{-} 1$

Average velocity:

$v e l o c i t y = \frac{\text{displacement}}{t i m e} = \frac{21}{10} = 2.1$ $m {s}^{-} 1$