Students will learn the meaning of speed, velocity and average velocity.

### Key Equations

**Average Velocity**

\begin{align*}v_{avg} & = \frac{\boldsymbol{\Delta} x}{\Delta t} \\ \end{align*}

Guidance |

Speed is the distance traveled divided by the time it took to travel that distance. Velocity is the instantaneous speed and direction. Average velocity is the displacement divided by the time. |

#### Example 1

Pacific loggerhead sea turtles migrate over 7,500 miles (12,000 km) between nesting beaches in Japan and feeding grounds off the coast of Mexico. If the average speed of a loggerhead is about 45 km/day, how long does it take for it to complete the distance of a one-way migration?

*Question:* \begin{align*}t = ?\end{align*} [days]

*Given:* \begin{align*}d = 12,000 \ km\end{align*}

\begin{align*}{\;} \qquad v_{avg} = 45 \ km/day\end{align*}

*Equation:* \begin{align*}v_{avg} = \frac{d}{t}\end{align*} therefore \begin{align*}t = \frac{d}{v_{avg}}\end{align*}

*Plug n’ Chug:* \begin{align*}t = \frac{d}{v_{avg}} = \frac{12,000 \ km}{45 \ km/day} = 267 \ days\end{align*}

*Answer:* \begin{align*}\boxed{\mathbf{267 \ days}}\end{align*}

### Time for Practice

- You drive the 10 miles to work at an average speed of 40 mph. On the way home you hit severe traffic and drive at an average speed of 10 mph. What is your average speed for the trip?