Fluid Mechanics

Fluid Mechanics

by Ronnie Lorilla

​What Is a Fluid?

​A fluid is a state of matter that yields to sideways or shearing forces. Liquids and gases are both fluids. Fluid statics is the physics of stationary fluids.

Multiple Choice

Which of the following is a fluid?

• helium
• ice
• iron
• gold

Multiple Choice

Which of the following statements is NOT correct?

• A fluid flows
• a fluid has a definite shape
• molecules of a fluid are free to move past each other
• a fluid changes it shape easily

Density

Multiple Choice

Why do some substances float on water?

• they are warmer than water
• they are cooler than water
• they are more dense than water
• they are less dense than water

Multiple Choice

Helium balloons rise on earth because

• helium is less dense than air
• helium is more dense than air
• helium is cooler than air
• helium is warmer than air

Multiple Choice

What units are used to measure Density?

• cm³/g
• g
• g/cm³
• cm³

Multiple Choice

What is the formula for Mass?

• Mass/Volume

• Density x Volume

• Mass/Density

Multiple Choice

What is the formula for Volume?

• Mass/Volume

• Density x Volume

• Mass/Density

Multiple Choice

What is this tool to get volume?

• triple beam balance
• ruler
• thermometer
• graduate cylinder

Multiple Choice

Blood has density equal to that of:

• Mercury

• Honey

• water

• glycerin

Pascal's Principle

• States that if the pressure in a container is increased at any point, the pressure increases at all points by the same amount.

Hydraulic devices and Pascal's principle

• Hydraulic devices use liquids to transmit pressure from one point to another.

• Because these liquids cannot be compressed into a much smaller space, they can pass on pressure better than gases can.

• Hydraulic devices can multiply forces.

• Use books to look at Figure 5 (pg 92)

Multiple Choice

Pressure is measured in what units

• Newtons
• m/s
• Pascals
• Moles

Multiple Choice

When pressure is applied to a confined fluid, the increase in pressure is transmitted equally to all parts of the fluid. This fact is called________.

• Pascal's Principle
• Newton's Principle
• Archimedes' Principle
• Bernoulli's Principle

Multiple Choice

What is the SI unit of pressure?

• Kg/m³

• Pa

• kg m^-3

• N m²

Multiple Choice

In what direction(s) does air exert pressure?

• everywhere
• no where
• there is no pressure
• downward

Multiple Choice

When force increases...

• pressure increases

• pressure decreases

• pressure stays the same

• pressure increases then decreases

Multiple Choice

When area increases...

• pressure increases

• pressure decreases

• pressure stays the same

• pressure increases then decreases

Multiple Choice

Fluids flow

• only when warmed up.

• from regions of low pressure to regions of high pressure.

• until evenly spread out.

• from high to low pressure.

Multiple Choice

What decreases as you go up in the atmosphere?

• Altitude
• Atmosphere
• Meteors
• Air Pressure

Multiple Choice

Several cans of different sizes and shapes are all filled with the same liquid to the same depth. Then,

• The pressure on the bottom of each can is the same

• The weight of the liquid on the bottom of each can is the same

• The least pressure is at the bottom of the can with the largest bottom area

• the force of the liquid on the bottom of each can is the same

Multiple Choice

What is the relationship between air pressure and altitude?

• There is no relationship.

• Air pressure increases as altitude increases.

• Air pressure decreases as altitude increases.

Buoyant Force

• Buoyant force is the upward force that keeps an object immersed in or floating on a fluid.

• Archimedes' principle is used to find buoyant force. Archimedes' principle states "The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces."

Multiple Choice

A buoyant force is a(n) ______ force 

• Upward
• Downward
• Side ways

Multiple Choice

A buoyant force is an upward force applied on an object by a 

• Substance
• Fluid
• Pressure
• Displacement

Multiple Choice

"Eureka" is greek for:

• Yippee!
• Look out!
• Hey you!
• I found it!

Multiple Choice

What was the principle Archimedes discovered?

• Principle of Volume
• Principle of Density
• Principle of Buoyancy
• Principle of Gravity

Multiple Choice

pushes an ice cube to the top of a glass of water

• buoyant force
• density
• a sinking object
• compressed air

Multiple Choice

Buoyancy is the tendency for objects to float in a fluid. We consider buoyancy the...

• Un-gravity force 
• Anti-gravity force
• Gravitational pull
• Downwards pull on an object

Multiple Choice

Archimedes' Principle states that... 

• The buoyant force acting on an object equals the volume of the fluid displaced by the object. 
• The buoyant force acting on an object equals the weight (force of gravity) of the fluid displaced by the object.
• The buoyant force acting on an object will always be equal. 

Multiple Choice

Which will result in positive buoyancy?

• When the buoyant force is greater than the force of gravity
• When the buoyant force is equal to the force of gravity
• When the buoyant force is less than the force of gravity

Multiple Choice

If an object sinks in a fluid, _____.

• the density of the fluid is greater than the density of the object
• the density of the fluid is less than the density of the object
• the density of the fluid is equal to the density of the object
• density has nothing to do with whether an object sinks or floats, only which state of matter the object is

Multiple Choice

An object will will be partially submerged in a fluid if ____.

• the weight of an object is greater than the buoyant force
• the weight of an object is less than the buoyant force
• the weight of an object is equal to the buoyant force
• the weight doesn't affect if an object sinks, only its state of matter

Multiple Choice

An object will NOT sink if its weight is ______ ______ _____ ______ ______ the buoyant force.

• Less than or equal to
• Greater than or equal to
• Similar to and almost equal
• Different from and almost equal

Fluids in Motion

• Fluids in motion have some properties in common.

• Fluids move faster through small areas than through larger areas, if the overall flow rate remains the same.

• But fluids also vary in the rate at which they flow.

Multiple Choice

According to equation of continuity, A₁V₁ = A₂V₂ = constant. The constant is equal to:

• Flow rate

• Volume of fluid

• Mass of fluid

• Density of fluid

Multiple Choice

Venturi meter is a device used to measure:

• Pressure of the fluid

• Viscosity of the fluid

• Velocity of the fluid

• Density of the fluid

Multiple Choice

If cross-sectional area of pipe decreases, the speed of fluid must increase according to:

• Continuity equation

• Bernoulli's equation

• Torricelli's theorem

• Venture relation

Multiple Choice

The study of properties of fluids in motion is called

• Fluids Study

• Fluids statics

• Fluids dynamics

• None

Multiple Choice

According to Bernoulli's theorem in a flowing liquid

• velocity is inversely proportional to pressure

• velocity is directly proportional to pressure

• velocity is directly proportional to volume

Multiple Choice

Which of the following is NOT an example of laminar flow?

• a river moving slowly in a straight line
• smoke rising upward in a smooth column through air
• water flowing evenly from a slight opened faucet
• smoke twisting as it moves upward from a fire

Multiple Choice

Which of the following properties is NOT a characteristic of an ideal fluid?

• laminar flow
• turbulent flow
• nonviscous
• incompressable

Multiple Choice

Bernoulli's equation cannot be used for flow of water in river because the flow is

• streamlined

• turbulent

• laminar

• viscous

Multiple Choice

Due to Bernoulli's principle, the pressure is ............... above an airplane's wing than below it.

• Lower

• Higher

Multiple Choice

States that as the velocity of a fluid increases, the pressure decreases.  This causes planes to fly . 

• Archimedes' Principle
• Bernoulli's Principle
• Pascal's Principle

Multiple Choice

Bernoulli's principle states that as the velocity of a fluid ______, the pressure exerted by the fluid ______

• increases; increases

• decreases; decreases

• increases; decreases

• decreases; increases

Multiple Choice

As the water falls from tap, its speed increases and cross sectional area:

• Decreases

• Increases

• become zero

• becomes Constant

Viscosity

• Viscosity is a liquid's resistance to flow and it depends on the particles attracton.

• The stronger the attraction between a liquid's particles, the more viscous the liquid is.

• Example: Honey flows more slowly than lemonade because honey has a higher viscosity than lemonade.

Multiple Choice

What is viscosity?

• A liquid's resistance to flow.
• a liquids flow.
• a liquid
• gas to solid.

Multiple Choice

Peanut butter is an example of a...

• High viscosity liquid

• Low viscosity liquid

• Isnt a liquid at all! Don't be silly.

Multiple Choice

Low viscosity can be described as...

• liquids that flow quickly

• liquids that flow slowly

Multiple Choice

Viscosity can be described as...

• a physical property of liquids

• a physical property of solids

• a chemical property of liquids

Multiple Choice

Terminal velocity is:

• The turbulent speed of an object that has been slowed by fluid

• The speed of laminar flow

• The drag force on a sphere going constant speed in a viscous fluid

• When the drag force equals the gravitational force acting on a falling body now going at a constant speed

​Surface Tension

• ​Cohesive forces between molecules cause the surface of a liquid to contract to the smallest possible surface area. This general effect is called surface tension.

  Attractive forces between molecules of the same type are called cohesive forces.

• Attractive forces between molecules of different types are called adhesive forces.

​Surface Tension

​Forces between atoms and molecules underlie the macroscopic effect called surface tension. These attractive forces pull the molecules closer together and tend to minimize the surface area. This is another example of a submicroscopic explanation for a macroscopic phenomenon.

​Capillarity Action

​The distortion of a liquid surface due to adhesive forces between the surface of the liquid and an adjacent solid surface. This can result in the liquid being pulled up or down a narrow tube

Multiple Choice

Ball pen works on principle of

• Boyle's law

• Newton's law

• Viscosity

• Capillarity and surface tension

Multiple Choice

What is the property of a liquid due to which its free surface tries to have minimum surface area?

• Viscosity

• Buoyancy

• Surface tension

• Rigidity

Multiple Choice

What's the difference between Cohesion and Adhesion?

• Cohesion is the attraction between the same substance and Adhesion is the attraction of different substances

• they both attract different substances

• They both attract the same substance

• They don't attract anything

Multiple Choice

Which is the effect of increase in the temperature on the surface tension of the liquid?

• it decreases

• it increases

• it remains the same

• None of the above

Multiple Choice

What is the main cause of capillarity?

• difference in weight of fluids

• pressure difference

• temperature difference

• velocity gradient

Multiple Choice

Which characteristic of water will allow a paperclip to remain floating on water when the paperclip is gently placed on top of the water?

• adhesion
• surface tension
• solvent properties
• nonpolar