Lesson 4 — More indepth on calculating speed

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Natuurkunde / ScheikundeMiddelbare schoolhavoLeerjaar 1

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Slide 1 - Diapositive

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


Slide 2 - Diapositive

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

Slide 3 - Diapositive

Recap

Slide 4 - Diapositive

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 - Diapositive

Discussing the homework

Slide 6 - Diapositive

Rearranging the formula for speed

Slide 7 - Diapositive

Rearranging the formula for speed
v=td
3=26

Slide 8 - Diapositive

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

Slide 9 - Diapositive

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

Slide 10 - Diapositive

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

Slide 11 - Diapositive

Discussing the homework

Slide 12 - Diapositive

Average speed & steady speed

Slide 13 - Diapositive

Speed:
How fast something is moving

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

Slide 14 - Diapositive

Average speed
avaragespeed=totaltimetotaldistance

Slide 15 - Diapositive

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

Slide 16 - Diapositive

Converting 
km/h <-> m/s 

Slide 17 - Diapositive

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 - Diapositive

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 - Diapositive

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 - Diapositive

km/h —> m/s
The speed x 1000/3600

m/s —> km/h
The speed x 3600/1000

Slide 21 - Diapositive

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 - Diapositive

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 - Diapositive

Homework
Do: 4.1 Workbook exercises

Slide 24 - Diapositive

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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