Lesson 5

• Science
• Middelbare school
• havo, vwo
• Leerjaar 2

TTO 2 – Science

Chapter 4. Speed

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 in m/s.

avaragespeed=​totaltime​​totaldistance​​

Exercise

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

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

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.

This lesson

• Practice exercises
  
• Precision and accuracy
  
• Significant figures
  

Learning goals

• calculate average speed
  
• Converte km/h <-> m/s
  
• Explain the difference between Precision and accurarcy
  
•  Explain what is meant by significant figures
  

Precision and accuracy

Precision:

How detailed your measurement is

Accuracy:

How correct your measurement is

Significant figures

Three measurements for a 400 meter sprint.

43 seconds

00043 seconds

43,03 seconds

Significant figures

The amount of meaning numbers in a measurement.

Usain bolt

Time:

Yohan Blake

Time:

Justin Gatlin

Time:

2012 olympics — 100 m sprint

Usain bolt

Time: 10 s

Yohan Blake

Time: 10 s

Justin Gatlin

Time: 10 s

Their 2012 times

1 significant number

Usain bolt

Time: 9.6 s

Yohan Blake

Time: 9.8 s

Justin Gatlin

Time: 9.8 s

Their 2012 times

2 significant number

Usain bolt

Time: 9.63 s

Yohan Blake

Time: 9.75 s

Justin Gatlin

Time: 9.79 s

Their 2012 times

3 significant number

Homework

Read: paragraph 4.2

Do: The workbook exercises of paragraph 4.2

Learning goals

• calculate average speed
  
• Converte km/h <-> m/s
  
• Explain the difference between Precision and accurarcy
  
•  Explain what is meant by significant figures