Average speed

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 2

Your speed will decide what distance 

you will travel every second.

Speed, distance & time

Speed	Time	Distance
10 km/h	1 h
10 km/h	5 h
50 km/h	3 h

The formula

For constant speeds, we have the following formula:

v is the speed in meters per second (m/s)

s is the distance in meters (m)

t is the time in seconds (s)

v=​t​​s​​

Eliod Kipchoge

On October 12th 2019, Eliod Kipchoge became the first human to complete a marathon 

(42.195 km) in under 2 hours!

What was his average running

speed? 

Use 1 hour and 59 min as his

finishing time.

What was the average running
speed of Eliod Kipchoge?

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.

Working on the exercises

Read: p. 8 - 11

Make: 1, 2, 4, 5, 8, 9

The formula

For constant speeds, we have the following formula:

v is the speed in meters per second (m/s)

s is the distance in meters (m)

t is the time in seconds (s)

v=​t​​s​​

There is a time interval of 1 second in between each picture, calculate the speed of the hiker

1. 0.74 m/s
2. 1,0 m/s
3. 1.35 m/s
4. 1.5 m/s

Johnny drives from his house to school. This trip is 4,5 km long and takes 10 minutes. Calculate his average speed

1. 450 km/h
2. 0.45 km/h
3. 27 km/h
4. 45km/h

A graph of the speed

On the y-axis (vertical),    we put the speed.

On the x-axis (horizontal), we put the time.

So what would constant speed look like?

A graph of the speed

Constant speed, means that v stays the same all the time!

Uniform motion!

A graph of the speed

Constant speed, means that v stays the same all the time!

How much distance is travelled here, in 100 seconds?

How much distance is travelled?

Acceleration.

How can we calculate the distance in this diagram? 

A graph of the speed

How can we calculate the distance in this diagram? 

--> We use the average

       speed

A graph of the speed

How can we calculate the distance in this diagram? 

--> We use the average

       speed

How can we calculate the average speed here?

A graph of the speed

How can we do this here?

--> We use the average

       speed

v​avg​​=​2​​v​inital​​+v​final​​​​

What is the average velocity/speed of this motion?

1. 10 m/s
2. 25 m/s
3. 40 m/s
4. 50 m/s

Type of motion?

Decelaration

Which part of this motion graph shows an acceleration?

1. from 0 to 5 sec
2. from 5 to 15 sec
3. from 15 to 15 sec

Working on the exercises

Read: p.26-30 

Make: section 3: 1,3,5,6,7,9+10

Not finished? --> Homework!

Finished? Start Test Yourself section 2 + 3