12.3 Moving In Fluids Flashcards
What is laminar flow?
a flow pattern where adjacent layers of fluid do not cross into each other
What is a turbulent flow?
a flow pattern where layers of fluid cross into each other, resulting in the formation of eddy currents
In an airplane what happens when turbulent flow happens on the wings?
turbulence
Why should laminar flow be used in e.g. food fillings be placed into food?
As otherwise air bubbles will show up?
When does laminar flow occur?
When travelling slowly either the fluid or object.
When does turbulent flow occur?
When travelling quickly either the fluid or object.
What else can cause turbulent flow?
If the radius of tube is quite small, density and viscosity
Explain density in this?
More density means more resistance to flow of motion and so smaller changes in will more are more likely to cause turbulent flow.
What is special about laminar flow?
Velocity stays constant at any point of fluid.
What is viscosity?
give example for low and high
Relates to fluids resistance to flow.
high = oil
low = water/ any gas
How does viscosity affect flow?
The lower the viscosity the easier it is for layers of fluid to slide over each other making it less likely to cause turbulent flow.
How can we compare viscosities? activity
Observing the rate of flow of substance through a funnel and a glass tube
What is the effect of viscosity called?
The viscous drag
What is viscous drag?
The resistance to motion due to contact between an object and a substance
What do we use to calculate force due to viscous drag?
Stokes Law
What happens to viscosity as temperature increases? Liquids
decrease
What happens to viscosity as temperature decreases in gases?
It will increase
Equation Stokes Law?
f = 6(pi)nrv f = force (viscous drag) n = viscosity of fluid r = radius of object v= speed of object
What does Stokes Law only apply to?
Small objects moving with laminar flow
Why does viscosity decrease with increasing temperature for liquids?
As molecules get more energy overcoming forces holding molecules together. This means liquid becomes more fluid.
Why does viscosity increase with greater temperature for gases?
Increases Ek meaning that the frequency of collisions of air particles is greater causing more resistance to flow. Each collision transfers more Ek and therefore even more collisions happen.
What forces act on a free falling sphere through a liquid.
W = weight U = upthrust F = viscous drag
What would be the equation (w u f) on a sphere falling downwards?
Fr = W - (U+F)
What would be the equation (w u f) on a sphere falling upwards?
Fr = U - (W+F)
When will a sphere reach terminal velocity?
When W = U + F or U = W+F depending on direction of movement
What is terminal velocity?
When resultant force becomes 0 and the sphere moves at constant velocity.
