# Lesson 4 — More indepth on calculating speed

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Slide 1: Tekstslide
Natuurkunde / ScheikundeMiddelbare schoolhavoLeerjaar 1

In deze les zitten 26 slides, met tekstslides.

## Onderdelen in deze les

#### Slide 1 -Tekstslide

This lesson
• Recap
• Discussing the homework
• Average speed & steady speed.
• Converting km/h <-> m/s

#### Slide 2 -Tekstslide

Goals
• You Know how to rearrange the formula for speed
• You are able to explain the difference between steady and average speed
• You are able to calculate average speed
• You Know how to convert km/h <-> m/s

Recap

#### Slide 4 -Tekstslide

Speed
Speed=timeDistance
v=td
New physical quantity:
Speed

Unit of Speed:
• m/s
• Km/h

Formula
• v: speed (meters/second) m/s)
• d: distance (meters) (m)
• t: time (seconds) (s)
The amount of distance something is traveling over a certain time.
Examples:
• A runner is running at a speed of 3/ms
• A car on the highway is driving at a speed of 120 km/h

#### Slide 5 -Tekstslide

Discussing the homework

#### Slide 6 -Tekstslide

Rearranging the formula for speed

#### Slide 7 -Tekstslide

Rearranging the formula for speed
v=td
3=26

#### Slide 8 -Tekstslide

Rearranging the formula for speed
v=td
Speed:
Distance:
Time:

#### Slide 9 -Tekstslide

Rearranging the formula for speed
v=td
Speed:
Distance:
d=vt
Time:

#### Slide 10 -Tekstslide

Rearranging the formula for speed
v=td
Speed:
Distance:
d=vt
Time:
t=vd

#### Slide 11 -Tekstslide

Discussing the homework

#### Slide 13 -Tekstslide

Speed:
How fast something is moving

Average speed
total distance divided
by total time
Traveling at a constant speed

#### Slide 14 -Tekstslide

Average speed
avaragespeed=totaltimetotaldistance

#### Slide 15 -Tekstslide

Exercise
You are an engineer at a formula one race track. One practice track has three parts to it. Part one with a length of 22,3 km. Part two with a length of 33,5 km. and part three with a length of 17,9 km. A race car speeds through this track two times. The first time it complets it in 19 minutes and 40.8 seconds the second time in 18 minutes and 27 seconds.

Calculate the average speed of this formula one race car.
avaragespeed=totaltimetotaldistance

Converting
km/h <-> m/s

#### Slide 17 -Tekstslide

Exercise
• A car travels 72km/h. What is that in m/s?
• A cyclist travels 7 m/s. What is that in km/h?

#### Slide 18 -Tekstslide

Exercise
• A car travels 72km/h. What is that in m/s?

• In one hour the car travels 72km = 72000 m
• One hour = 3600 seconds
• So in 3600 seconds it travels 72000 m
• Then in 1 second it travels 72000/3600 = 20 m/s
• So a speed of 72km/h converts to 20 m/s

#### Slide 19 -Tekstslide

Exercise
• A cyclist travels 7 m/s. What is that in km/h?

The cyclist travels 7 meters in one second
There are 3600 seconds in one hour
So in one hour the cyclist travels 7m x 3600 = 25200m
25200m = 25.2 km. the cyclist travels 25.2 km in on hour.
So a speed of 7 m/s converts to 25km/h.

#### Slide 20 -Tekstslide

km/h —> m/s
The speed x 1000/3600

m/s —> km/h
The speed x 3600/1000

#### Slide 21 -Tekstslide

Exercise
Convert a speed of 38 km/h to m/s
Convert a speed of 1.5 m/s to km/h
km/h —> m/s
The speed x 1000/3600

m/s —> km/h
The speed x 3600/1000

#### Slide 22 -Tekstslide

Exercise
Convert a speed of 38 km/h to m/s      =      10.55 m/s
Convert a speed of 1.5 m/s to km/h      =      5.4 km/h
km/h —> m/s
The speed x 1000/3600

m/s —> km/h
The speed x 3600/1000

#### Slide 23 -Tekstslide

Homework
Do: 4.1 Workbook exercises

#### Slide 24 -Tekstslide

Goals
• You Know how to rearrange the formula for speed
• You are able to explain the difference between steady and average speed
• You are able to calculate average speed
• You Know how to convert km/h <-> m/s
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