## Ngā Whāinga Ako

- Name the metric units of
**distance**,**time**and**speed**and give their symbols. - Define the term speed.
- Calculate the
**average speed**of objects. Use $v=d/t$.

## What is Speed?

You know that someone who finishes a race in the shortest time is the fastest. That they have the highest speed.

Speed is the amount of distance covered in some amount of time.

## What is Speed?

- Cars display their speed in
*kilometers per hour* - In Physics we prefer to give speed in the
**number of meters**travelled in**one second**. - We call this
*meters per second*.

## Calculating Speed

In order to determine speed we need to know two things!

**Distance**: has unit meters (m) and is represented by symbol $d$ in equations.**Time**: has unit seconds (s) and is represented by symbol $t$ in equations.

## Speed vs Velocity

**Speed**is a measure of distance covered in a certain amount of time.- e.g 13 meters per second

**Velocity**includes a direction- e.g. 13 meters per second
**east**

- e.g. 13 meters per second

## How to Calculate Velocity

\begin{aligned}
velocity &= \frac{\text{change in distance}}{\text{change in time}} \\
v &= \frac{\Delta d}{\Delta t} \\
\end{aligned}

It is measured in meters per second, also shown as $\frac{m}{s}$ or $ms^{-1}$.

## How Do We Solve Problems?

- Knowns
- Unknowns
- Formula
- Substitute
- Solve

## Question 1: Velocity

A rock climber climbs 15 meters in 5.48 seconds. What velocity was he travelling?

## Question 1: Answer

**Knowns:**$\text{distance (d)}=15m$, $\text{time (t)} = 5.48s$**Unknowns:**$\text{velocity (v)}$**Formula:**$v = \frac{\Delta d}{\Delta t}$**Substitute:**$v = \frac{15}{5.48}$**Solve:**$v = 2.74\frac{m}{s}$

## Question 2

- Mr Le Sueur ran 4.61km in 21 minutes and 16 seconds. How fast did he run?
**Hint:**Convert the time and distance to Standard International Units

## Question 2: Answer

**Knowns:**$\text{distance (d)} = 4.61km = 4610m$, $\text{time (t)} = 21min, 16s = 1276s$**Unknowns:**$\text{velocity (v)}$**Formula:**$v = \frac{\Delta d}{\Delta t}$**Substitute:**$v = \frac{4610}{1276}$**Solve:**$v = 3.61\frac{m}{s}$

## Question 3

- Mr Le Sueur ran at $1.51\frac{m}{s}$ for 1hr, 18min and 11 seconds. How far did he run?
**Hint:**Convert the time to Standard International Units

## Question 3: Answer

**Knowns:**$\text{velocity (v)} = 1.51\frac{m}{s}$, $\text{time (t)} = 1hr, 18min, 11s = 4691s$**Unknowns:**$\text{distance (d)}$**Formula:**$v = \frac{\Delta d}{\Delta t}$**Substitute:**$1.51 = \frac{d}{4691}$**Solve:**$1.51 \times 4691 = d = 7083.41m$

## Mahi Kāinga

Due Monday, August 24th: Mahi Kāinga Booklet Q2, Q3, Q1