2.4 graphs and air resistance

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 2

How do you calculate speed?

When making a graph of the time it takes to go from home to school,
what labels do I put on the axis?

1. x-axis: speed v y-axis: time t
2. x-axis: distance x y-axis: time t
3. x-axis: time t y-axis: speed v
4. x-axis: time t y-axis: distance x

Distance-time graph

Now draw this graph in your notebook 
with distance in km on the y-axis
and time in min on the x-asis.

Draw the following:
On the first track I ride 3 km in 15 min at constant speed.

Then I need to wait at a traffic light for 5 min. 

Then I need to speed up and ride 3 km in 10 min. 

I cycle 3 km in 15 min,
what is my speed in SI units?

Calculation tactics

Given:

Asked:

Formula:

Calculation:

Answer:

Skill: Reading graphs.
What needs explanation?

1. How are the axes labeled?
2. What is the scale on the axes?
3. What is the slope and shape of the graph?
4. Where does the graph start and end?

Which questions are there still about unit 2.3 (acceleration)

Learning objectives unit 1

- Calculating speed using the problem solving procedure.

- Drawing a x,t-graph based on data given / measurements.

Video slide

after this: Brian Cox visits the world's biggest vacuum

Free Fall of a Bowling Ball and a set of feathers.

00:25

What does vacuum mean?

01:27

Which object falls fastest
when air resistance
is significant (= plays a role)?

1. The feathers
2. The bowling ball
3. No difference in speed

02:28

What do we call
the force on any object near the Earth's surface?

03:00

Which object falls fastest
when air resistance
is NOT significant (= plays a role)?

1. The feathers
2. The bowling ball
3. No difference in speed

03:24

Why is there no difference in speed when the feathers and bowling ball fall now?

04:41

According to Newton: a freely falling object has a constant acceleration.

1. TRUE
2. FALSE
3. IDK

The acceleration of a freely falling object near the Earth
is 10 m/s . It took 15 s for the objects to fall.
a) Calculate the speed with which they hit the bottom.
b) Calculate the height from which they fell.
Tip: Use the average speed.

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