Airfriction & terminal velocity

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 2,3

Airfriction & terminal velocity

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You know which factors have an impact on airfriction 

You can explain the concept of terminal velocity

You can explain how the forces at work on a parachutist and the corresponding v-t graph are related with each other

Free fall

Definition:

In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it.

The gravitational force is the only force at work, so there is no air friction at all.

The term Free fall is often not used correctly of which the article of the NOS is an example. The free fall of the lift was not really a free fall since only the hoisting cable snapped. The other cable were still attached. Besides that the lift shaft is filled with air, so there was both air friction and friction from the other cables.

The people inside did survive their fall.

.

NOS, 

19-11-2019

Upload your v-t graph

Explanation

You can use this text to get a better understanding on how the v-t graph is interrelated with the forces at work.

Airfriction (drag)

Can you explain why the v-t graph of a falling object will look like the graph below?

When there would be no airfriction the graph would follow the black line (see the graph on the right)

Airfriction 

The amount of air friction is influenced by: 

• the velocity of the object
  
• the frontal area of the object
  
• the density of the air
• the aerodynamic shape of an object
  

Drag Formula

         

•           - velocity 
•           - frontal area (cross section)
  
•           - density
•            - aerodynamic value (drag coefficient)

F​D​​=​2​​1​​⋅C​D​​⋅A⋅ρ⋅v​2​​

C​D​​

(m​2​​)

A

ρ

v

(​m​3​​​​kg​​)

(​s​​m​​)

Assignments

Question 1

Draw a x-t (distance against time) and a v-t (speed against time) graph of a falling rock without any air friction.

Question 2

Draw a x-t (distance against time) and a v-t (speed against time) graph of a falling rock with air friction.

Question 3

Look at both graphs. These graphs describe the motion of a falling object.

1. How can you make up out of both graphs that the air friction cannot be neglected?
2. What is the velocity at t = 0 s.
   
3. What is the acceleration at t = 0 s.

UPLOAD
Answer 1, 2 and 3 here