# An object travels North at 7 m/s for 9 s and then travels South at 6 m/s for  2 s. What are the object's average speed and velocity?

Aug 26, 2017

$\text{Average Speed} = \frac{75}{11} \frac{m}{s}$
$\text{Average Velocity} = \frac{51}{11} \frac{m}{s}$

#### Explanation:

Object Travel North
Time taken = 9 s
speed = 7 m/s
Travel Distance = $s p e e d \cdot t i m e = 7 \cdot 9 = 63 m$

Object Travel South
Time taken = 2 s
speed = 6 m/s
Travel Distance = $s p e e d \cdot t i m e = 6 \cdot 2 = 12 m$

$\text{Average Speed"= "total distance "/ "total time} = \frac{63 + 12}{9 + 2} = \frac{75}{11} \frac{m}{s}$

Displacement
object travel 63 m towards North and 12 m towards south
$\to t a l \mathrm{di} s p l a c e m e n t = 63 - 12 = 51 m$

$\text{Average Velocity"="Total displacement"/"total time} = \frac{63 - 12}{9 + 2} = \frac{51}{11} \frac{m}{s}$