Physics Chapter on Fluid Mechanics
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Questions and Answers

What defines atmospheric pressure?

  • The weight of the air above a surface in kilograms
  • The total weight of all gases in the atmosphere
  • The pressure applied by the wind on a surface
  • The force per unit area exerted by the weight of air above a surface (correct)

What happens to pressure if the surface area is increased while keeping the force constant?

  • Pressure decreases (correct)
  • Pressure remains the same
  • Pressure increases
  • Pressure fluctuates

At what depth does the pressure of water affect a scuba diver's body the most?

  • At the surface of the water
  • At moderate depths
  • At extreme depths (correct)
  • Pressure is consistent throughout the dive

Which of the following best describes a fluid?

<p>A material that can flow and change shape due to free-moving particles (A)</p> Signup and view all the answers

How is pressure defined mathematically?

<p>Force divided by area (D)</p> Signup and view all the answers

What is a potential consequence of ascending too quickly while scuba diving?

<p>Formation of gas bubbles in the blood, known as the bends (D)</p> Signup and view all the answers

What is the SI unit for atmospheric pressure?

<p>Kilopascals (kPa) (C)</p> Signup and view all the answers

How does atmospheric pressure change with elevation?

<p>It decreases with rising elevation (D)</p> Signup and view all the answers

What is the upward force exerted on an object immersed in a fluid called?

<p>Buoyant force (D)</p> Signup and view all the answers

When will an object experience positive buoyancy?

<p>When the buoyant force is greater than its weight (D)</p> Signup and view all the answers

What does Archimedes’ principle state about the buoyant force on a submerged object?

<p>It is equal to the weight of the fluid displaced by the object. (B)</p> Signup and view all the answers

An object sinks in water when:

<p>Its weight is greater than the buoyant force. (A)</p> Signup and view all the answers

A cube with a mass of 1 kg has a volume of $1176 ext{cm}^3$. What is its density?

<p>0.9 g/cm³ (A)</p> Signup and view all the answers

If a toy boat with a mass of 850 g displaces 900 g of seawater, what will happen?

<p>The boat will float. (A)</p> Signup and view all the answers

What equation gives the weight of an object?

<p>W = m x g (B)</p> Signup and view all the answers

A material with a density less than water will:

<p>Float in water. (C)</p> Signup and view all the answers

What is the relationship between pressure, force, and area in fluids?

<p>Pressure is defined as force divided by area. (C)</p> Signup and view all the answers

According to Pascal's Principle, how is pressure transmitted in a confined fluid?

<p>Pressure remains constant throughout the fluid. (A)</p> Signup and view all the answers

If a force of 7,500 N is applied to a piston with an area of 0.05 m², what is the pressure exerted by the piston?

<p>375,000 Pa (B)</p> Signup and view all the answers

In a hydraulic lift, if the area of the small piston is 0.2 m² and it supports a car weighing 12,000 N on a large piston with an area of 0.9 m², what force must be applied to the small piston?

<p>2,667 N (A)</p> Signup and view all the answers

Why must the small piston move over a greater distance than the large piston in a hydraulic system?

<p>It compensates for the difference in force produced. (C)</p> Signup and view all the answers

What is the work done by each piston in a hydraulic system if the pressure is constant?

<p>Work is the same for both pistons. (A)</p> Signup and view all the answers

What is the concept that explains that a small force applied at one end of a piston can create a large force at another end?

<p>Pascal's Principle (A)</p> Signup and view all the answers

If the area of the shaft of a hydraulic lift is 80.0 cm² and the area of the piston that forces liquid into the system is 2.0 cm², what can be inferred about the pressure relationship?

<p>Pressure is the same throughout the system. (A)</p> Signup and view all the answers

What happens to the buoyant force when the weight of the water displaced is greater than the weight of the boat?

<p>The boat remains afloat. (C)</p> Signup and view all the answers

Which statement correctly describes the effect of moving air on pressure?

<p>Moving air exerts less pressure than stationary air. (C)</p> Signup and view all the answers

According to Bernoulli’s Principle, what happens to the pressure of a fluid when its velocity increases?

<p>The pressure decreases. (A)</p> Signup and view all the answers

In the presence of a high wind, what effect does the air velocity above the roof of a house have?

<p>It decreases the pressure on the roof. (C)</p> Signup and view all the answers

What does viscosity measure regarding a fluid?

<p>Its resistance to flow. (D)</p> Signup and view all the answers

How does an increase in temperature affect the viscosity of a liquid?

<p>It decreases viscosity. (B)</p> Signup and view all the answers

What type of liquids is characterized by having low viscosity?

<p>Water and alcohol. (A)</p> Signup and view all the answers

What phenomenon is demonstrated when blowing into a funnel with a ball placed inside?

<p>The ball remains in the funnel due to lower air pressure above. (A)</p> Signup and view all the answers

Flashcards

What defines a fluid?

The ability of a material to change its shape based on the movement of its individual particles (atoms, molecules, or ions).

What is pressure?

The force exerted per unit area of a surface.

What is atmospheric pressure?

The force per unit area exerted by the weight of the air above a surface, typically measured at sea level.

How does pressure change with fluid depth?

As the depth of a fluid increases, the pressure also increases.

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What is a Pascal?

The pressure unit in the International System of Units, equal to one Newton per square meter (N/m²).

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What is an atmosphere (atm)?

The standard unit for atmospheric pressure, equal to approximately 101.3 kilopascals (kPa) or 14.7 pounds per square inch (psi).

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What are "the bends"?

A condition caused by gas bubbles forming in the bloodstream, often during rapid ascent from deep underwater dives, leading to pain and potentially serious complications.

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What is hydrostatic pressure?

The pressure exerted by the weight of all the fluid above a certain depth.

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What is buoyant force?

The upward force exerted on an object immersed in a fluid.

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What is Archimedes' Principle?

The buoyant force is equal to the weight of the fluid displaced by the object. This means the object pushes aside an amount of fluid equal to its own volume.

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What is buoyancy?

The ability of a fluid (liquid or gas) to exert an upward force on objects immersed in it. This force determines whether an object floats, sinks, or hovers.

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What happens if an object has 'positive buoyancy'?

The object will float because the buoyant force is greater than its weight.

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What happens if an object has 'negative buoyancy'?

The object will sink because its weight is greater than the buoyant force.

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What happens if an object has 'neutral buoyancy'?

The object will 'hover' in the fluid because its weight is equal to the buoyant force.

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How do 'density' and 'buoyancy' determine if something sinks or floats?

Whether an object sinks or floats depends on its density compared to the fluid. It also depends on the buoyant force acting on it.

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Pressure in Confined Fluids

Pressure in a confined fluid is the same throughout, pushing equally on all walls.

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Pascal's Principle

Pressure exerted on a fluid is transmitted evenly in all directions.

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Pressure in a Cylinder

The force applied to a piston divided by its area, calculated as P = F/A

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Hydraulic Systems

Hydraulic systems use Pascal's Principle to create a mechanical advantage. A small force applied to a small piston creates a large force on a larger piston.

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Work Done in Hydraulic Systems

In a hydraulic system, the work done by each piston is the same, even if the forces and distances are different.

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Force Relationship in a Hydraulic System

The force exerted on a piston (F1) is equal to the force exerted on another piston (F2) multiplied by the ratio of their areas (A1/A2). F1 = F2 x (A1/A2)

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Hydraulic Lift

A hydraulic lift uses two pistons connected by fluid. A smaller force on the small piston is amplified to lift a heavier object on the larger piston.

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Calculating Force in a Hydraulic Lift

To calculate the force needed to lift a weight using a hydraulic lift, use the formula F1 = F2 x (A1/A2), where F1 is the force on the small piston, F2 is the weight of the object, A1 is the area of the small piston, and A2 is the area of the large piston.

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Viscosity

The ability of a fluid to resist flow, caused by the interaction between its molecules. It's often described as the 'internal friction' of a fluid.

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Low Viscosity Liquids

Liquids with low viscosity flow easily, like water or alcohol.

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High Viscosity Liquids

Liquids with high viscosity resist flow, like syrup or honey.

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Temperature's Effect on Viscosity

Increasing temperature decreases viscosity, making fluids flow more easily. This is because the molecules have more kinetic energy and move more freely, reducing friction.

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Temperature's Effect on Viscosity

Decreasing temperature increases viscosity. Molecules move slower with less kinetic energy, increasing friction.

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Bernoulli's Principle

As the velocity (speed) of a fluid increases, the pressure it exerts decreases.

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Bernoulli Effect

The principle that explains how things can be lifted or held in place by moving air, like a ball in a funnel or an airplane wing.

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Moving Air Pressure

When a fluid (especially air) is moving, it exerts lower pressure than a stationary fluid.

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Study Notes

Introduction to Fluids

  • Fluids are both liquids and gases
  • Individual particles (atoms, molecules, ions) change positions, causing flow

Pressure

  • Pressure = Force/Area
  • Smaller area = higher pressure
  • Larger area = lower pressure

Example with Shoes

  • Flat shoes have a large surface area, distributing weight (low pressure).
  • High heels have a small surface area, exerting high pressure

Pressure and Thumb Tacks

  • Small area of tack creates high pressure, causing a puncture
  • Larger area like a dull knife creates lower pressure

Atmospheric Pressure

  • Pressure exerted by the air above a surface
  • It decreases with altitude due to less air above
  • 14.7 pounds per square inch (psi) at sea level

Air Pressure Varies with Elevation

  • See table for pressure at various locations

Pressure in Fluids

  • Pressure increases with depth
  • Water forced out goes farther with increasing depth

Why Pressure Increases with Depth

  • Gravity pulls fluid particles downwards
  • As depth increases, there's an increasing column of water above

The Bends

  • Scuba divers may experience the bends if nitrogen forms bubbles in the blood when surfacing too quickly
  • Water is much denser than air
  • Deeper dives and slower ascents increase pressure, potentially dangerous

Common Units of Pressure

  • Pascal (Pa) = SI unit (1 N/m²)
  • Pound per square inch (psi)
  • Bar
  • Tor
  • Atmosphere (atm)

Pressure in Confined Fluids

  • Pressure is the same throughout a confined liquid (neglecting gravity)
  • Force applied to a confined fluid is transmitted evenly throughout

Pascal's Principle

  • Pressure applied to a confined fluid is transmitted evenly throughout the fluid
  • Small force over a small area can create a large force over a large area

Hydraulic Systems

  • Use Pascal's principle for mechanical advantage
  • Force exerted on a small piston creates an amplified force on a larger piston
  • Principle used in hydraulics such as car brakes and jacks

Hydraulic Brakes

  • System of pipes and cylinders uses hydraulic fluid to transmit force

Pressure-Force Problems (Pascal's Principle)

  • Pressure is constant in a closed system
  • Force on smaller area proportionally reduced by larger piston area

Practice Problems (Hydraulic Lifts)

  • Applying force to a small piston to lift a large object
  • Pressure and area are crucial factors to consider

Buoyancy

  • Ability of a fluid to push up on immersed objects

Archimedes' Principle

  • Upward force experienced by immersed objects equal to weight of fluid displaced

Sink or Float Problems

  • Substances sink or float based on their density relative to the fluid
  • Buoyant force vs weight of the object

Density of Ships

  • Ships float even if mainly steel because of air pockets
  • Density includes the weight of contained air

Air Pressure

  • Air exerts pressure equally in all directions
  • Moving air can reduce upward pressure on surfaces, like airplane wings

Bernoulli's Principle

  • As fluid velocity increases, pressure decreases.
  • Conservation of energy

Bernoulli Effect (Applications)

  • Explains how air pressure affects objects like ping-pong balls and airplane wings

Viscosity

  • Resistance of a fluid to flow

Low vs. High Viscosity Liquids (Table)

  • Liquids with different flow properties
  • Viscosity varies by temperature

Viscosity and Temperature

  • Higher temperature leads to lower viscosity
  • Lower temperature leads to higher viscosity

Molasses Disaster

  • An example highlighting the force resulting from a high-viscosity substance, in this case molasses.
  • Provided links for in depth study of all materials presented on factors affecting fluids and properties of fluids

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Ch. 14-2 Properties of Fluids PDF

Description

Test your knowledge on fluid mechanics with this quiz, which covers key concepts such as atmospheric pressure, buoyancy, and the effects of depth while scuba diving. Explore how pressure is defined both mathematically and in real-world applications. Perfect for students studying physics or anyone interested in understanding the principles of fluids.

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