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Speed, Velocity

Ngā Whāinga Ako

  1. Name the metric units of distance, time and speed and give their symbols.
  2. Define the term speed.
  3. 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?


Calculating Speed

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


Speed vs Velocity


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?

  1. Knowns
  2. Unknowns
  3. Formula
  4. Substitute
  5. Solve

Question 1: Velocity

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

Mr Le Sueur @ Cattlestop Crag


Question 1: Answer

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

Question 2

CHS Trail Running Club


Question 2: Answer

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

Question 3

Mt Thomas


Question 3: Answer

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

Mahi Kāinga

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


Do Now: sciPAD Page 8, 9, 10