# An object travels North at 4 m/s for 5 s and then travels South at 9 m/s for  2 s. What are the object's average speed and velocity?

##### 2 Answers
Jan 14, 2018

Average speed = $5.42 \frac{m}{s}$
Average velocity = $0.28 \frac{m}{s}$

#### Explanation:

We know that average speed = total distance covered/total time taken.

So,total distance covered in this case in 7 seconds is $\left(4 \cdot 5\right) + \left(9 \cdot 2\right)$ meters or, 38 meters,hence average speed is $\frac{38}{7}$ $\frac{m}{s}$ or, $5. 42 \frac{m}{s}$

Now,avergae velocity = total displacement/total time taken

Here,the object has gone $20$meters to north and $18$ meters to south,hence displacement = $\left(20 - 18\right) m \mathmr{and} 2 m$ (taking towards north to be positive)

Hence average velocity is $\frac{2}{7} \frac{m}{s}$ or, $0.28 \frac{m}{s}$

Jan 14, 2018

velocity=$\frac{2}{7} \frac{m}{s}$
speed=$5.4 \frac{m}{s}$