# An object travels North at 1 m/s for 3 s and then travels South at 12 m/s for 7 s. What are the object's average speed and velocity?

Mar 1, 2018

See the explanation below

#### Explanation:

The total distance travelled is

$d = \left(1 \cdot 3\right) + \left(12 \cdot 7\right) = 3 + 84 = 87 m$

The total time is

$t = 3 + 7 = 10 s$

The average speed is $= \frac{d}{t} = \frac{87}{10} = 8.7 m {s}^{-} 1$

The distance travelled is

${d}_{1} = 1 \cdot 3 - 12 \cdot 7 = 3 - 84 = - 81 m$

The time is the same

$t = 10 s$

The average speed is

$= | {d}_{1} \frac{|}{t} = \frac{81}{10} = 8.1 m {s}^{-} 1$