5.2.1+2 Average Speed

Your speed will decide what distance 
you will travel every second.
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NatuurkundeMiddelbare schoolhavo, vwoLeerjaar 2,3

This lesson contains 31 slides, with interactive quizzes, text slides and 8 videos.

time-iconLesson duration is: 50 min

Items in this lesson

Your speed will decide what distance 
you will travel every second.
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Slide 2 - Slide

Two kinds of speed
Instantaneous and average speed

The instantaneous speed is the speed of an object at a particular moment (instant) in time.

The average speed on the other hand can be calculated by dividing the distance travelled by the total time it has taken to do so. 

The next two videos will explain 
to you how to calculate the instantaneous speed and the average speed.

Slide 3 - Slide

Daphne Schippers can run very hard. But her speed is not constant. 

To calculate her average speed you can divide the total distance by the total time. 

To calculate the instantaneous speed at any one time, you will need to make use of a graph of her motion at every instance of her run.

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Slide 5 - Video

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Slide 8 - Video

Speed of sound
The speed of sound is 343 m/s (in air)

You can hear sounds with a frequency in between 20 Hz and 20 kHz

Sounds is a form of energy, like light, heat or electricity.
The speed of sound depends on the medium through which it travels 
(air = 343 m/s, water = 1400 m/s, steel = 6000 m/s). It needs matter though, so it will not travel through a vacuum.

Slide 9 - Slide

Use the speed of sound to calculate the distance of a lightning strike from which you hear the thunder 8,5 seconds later

Slide 10 - Open question

Speed of light
The speed of sound is 300.000 km/s

Because of this very high speed, light will travel enormous distances in the blink of an eye. This distance is expressed in light years.

A light year is not a measure of time. A lightyear is the distance light can travel in one year (s = v . t = 300.000 km/s . 365 dg . 24 h/dg .3600 s/h= 9.460.800.000.000 km= aproximately 9,5 trillion kilometres

Slide 11 - Slide

Sunlight takes eight minutes to travel from the sun to the earth, how far does it need to travel?

Slide 12 - Open question

Clara and Rob live 50 kilometers from each other.
They want to meet up and leave home at 8 o'clock in the morning.
Clara travels with a speed of 6 km/h, while Rob travels with a speed of 4 km/h. How far from home do they meet each other and at what time?

Slide 13 - Open question

Quantities and units

A quantity is something you can measure

A unit is the measurement of the magnitude of the quantity


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Quantities and their standard units

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Scalars & vectors
Scalars are quantities which are described by magnitude only.

Vectors are quantities which are described  by both a magnitude and a direction

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Slide 20 - Video

Distance 
the total distance travelled is 12 m, but in the end you end up in exactly the same spot where you have started so the final displacement is zero meter

Slide 21 - Slide

Distance 
Distance is a scalar quantity that refers to
 "how much ground an object has covered"
without any regard for the direction of this motion.
(a scalar quantity)

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Displacement
the total distance travelled is 12 m
But you end up at exactly the same spot from where you started.
Thereforce the total displacement will be zero meters in this case.

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Displacement 
Displacement is a vector quantity that 
refers to "how far out of place an object is".

It is the object's overall change in position.
It refers to the distance moved in a particular direction.
(a vector quantity)

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Slide 25 - Video

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Speed 
Speed is the rate of change of distance of an object

Depends on the distance traveled and the times it takes to travel that distance


averagespeed=totaltimetotaldistancetravelled
(a scalar quantity)

Slide 27 - Slide

Velocity 
Velocity of an object is the distance it has moved in a particular direction

So when talking about velocity, you should always mention a direction in your phrasing, like south, to the right etc..


velocity=totaltimechangeindisplacement
(a vector quantity)

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Slide 29 - Video

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Slide 31 - Video