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Questions and Answers
What is the buoyant force acting on an object immersed in a fluid?
What is the buoyant force acting on an object immersed in a fluid?
Which condition indicates an object will float?
Which condition indicates an object will float?
If an object has a weight of 12 N and a buoyant force of 15 N acting on it, what will happen to the object?
If an object has a weight of 12 N and a buoyant force of 15 N acting on it, what will happen to the object?
What is the formula to calculate the weight of an object?
What is the formula to calculate the weight of an object?
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What happens to objects with negative buoyancy?
What happens to objects with negative buoyancy?
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What occurs at neutral buoyancy?
What occurs at neutral buoyancy?
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If a toy boat has a mass of 850 g and displaces 900 g of sea water, will it sink or float?
If a toy boat has a mass of 850 g and displaces 900 g of sea water, will it sink or float?
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Which of the following best describes Archimedes' Principle?
Which of the following best describes Archimedes' Principle?
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What causes the upward force keeping a ball in an upside-down funnel when air is blown into it?
What causes the upward force keeping a ball in an upside-down funnel when air is blown into it?
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How does temperature affect the viscosity of a liquid?
How does temperature affect the viscosity of a liquid?
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Which of the following statements best describes viscosity?
Which of the following statements best describes viscosity?
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What happens to the pressure exerted by moving air compared to still air?
What happens to the pressure exerted by moving air compared to still air?
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Which type of liquid is considered to have high viscosity?
Which type of liquid is considered to have high viscosity?
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What causes the roof of a house to lift off during high winds?
What causes the roof of a house to lift off during high winds?
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Which of the following best describes Bernoulli's Principle?
Which of the following best describes Bernoulli's Principle?
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If a liquid has low viscosity, what characteristic does it have?
If a liquid has low viscosity, what characteristic does it have?
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What defines a fluid according to its physical properties?
What defines a fluid according to its physical properties?
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How does surface area affect pressure when a force is applied?
How does surface area affect pressure when a force is applied?
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What is atmospheric pressure at sea level?
What is atmospheric pressure at sea level?
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What happens to atmospheric pressure as elevation increases?
What happens to atmospheric pressure as elevation increases?
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Why does a scuba diver experience increased pressure when diving deeper?
Why does a scuba diver experience increased pressure when diving deeper?
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What can occur if a scuba diver ascends too quickly?
What can occur if a scuba diver ascends too quickly?
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What is the unit of pressure defined in the SI system?
What is the unit of pressure defined in the SI system?
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How does the density of water compare to that of air?
How does the density of water compare to that of air?
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What happens to the pressure in a confined fluid when an external force is applied to a piston?
What happens to the pressure in a confined fluid when an external force is applied to a piston?
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If a small force is applied over a small area of a piston in a hydraulic system, what can be inferred about the force on a larger piston?
If a small force is applied over a small area of a piston in a hydraulic system, what can be inferred about the force on a larger piston?
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How is work defined in relation to the forces acting on the pistons in a hydraulic system?
How is work defined in relation to the forces acting on the pistons in a hydraulic system?
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In the example given, what is the force exerted on the first piston (F1) if the second piston (F2) exerts a force of 7,500 N with their respective areas of 0.05 m² and 0.01 m²?
In the example given, what is the force exerted on the first piston (F1) if the second piston (F2) exerts a force of 7,500 N with their respective areas of 0.05 m² and 0.01 m²?
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What force needs to be applied to the small piston if a car weighing 12,000 N is sitting on a large piston with an area of 0.9 m²?
What force needs to be applied to the small piston if a car weighing 12,000 N is sitting on a large piston with an area of 0.9 m²?
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Which statement correctly describes Pascal’s Principle?
Which statement correctly describes Pascal’s Principle?
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How does the distance moved by the small piston compare to the distance moved by the large piston in a hydraulic system?
How does the distance moved by the small piston compare to the distance moved by the large piston in a hydraulic system?
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What key factor is responsible for the operation of hydraulic systems?
What key factor is responsible for the operation of hydraulic systems?
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Study Notes
Properties of Fluids
- Fluids are liquids and gases.
- Individual particles (atoms, molecules, ions) of fluids can change positions. This allows them to flow.
Pressure
- Pressure is force exerted per unit area.
- Pressure = Force / Area
- Smaller area = greater pressure for the same force.
- Larger area = smaller pressure for the same force.
Example with Shoes
- Shoes with wide soles distribute weight over a large area.
- Shoes with narrow soles (high heels) exert more pressure on the surface.
- A 100-pound person on an average shoe applies 5 pounds per square inch.
- A 100-pound person on a high heel applies over 400 pounds per square inch.
Consider a thumb tack
- A thumb tack exerts high pressure due to its small contact area.
- Pressure is inversely proportional to the area, given a constant force.
Atmospheric Pressure
- Atmospheric pressure is the force per unit area exerted by the weight of the air above a surface.
- At sea level, air pressure is 14.7 pounds per square inch.
- Air pressure decreases at higher altitudes.
- Air pressure is less in higher elevation; hence, it is harder to breathe in the mountains.
Air Pressure Varies with Elevation
- Air pressure varies with altitude (elevation).
- Sea level has higher air pressure compared to higher elevations, such as the highest mountain in the US (Mt. McKinley) or Mt. Everest.
Pressure in Fluids
- Pressure in fluids increases with depth.
- Deeper the fluid, higher the pressure.
- Water exerts greater pressure at the bottom of the tin can compared to the top.
Why does pressure increase with depth?
- Gravity pushes particles down.
- Deeper depths have more fluid above the object.
- This pushes down with a greater force causing a greater pressure.
The Bends
- The bends occur when divers experience rapid decompression.
- Nitrogen in the blood creates bubbles that can cause pain and death.
Some Common Units of Pressure
- Pascal (Pa) = 1 N/m² (SI unit)
- Pounds per square inch (psi) = 6,891 Pa
- Bar = 105 N/m² ≈ 1 atm
- Torr = 1 mm Hg ≈ 1 kPa
- 1 atm = 101.3 kPa = 760 mm Hg = 29.92 in Hg = 14.70 psi
Pressure in Confined Fluids (Pascal's Principle)
- In confined fluids (neglecting gravity) pressure is the same throughout the container.
- Pressure equals force divided by area; a small force applied to a small area can produce a large force on a larger area.
- Pascal's principle is fundamental to hydraulic systems using fluids.
Hydraulic Systems
- Hydraulic systems use Pascal's Principle to multiply forces.
- A small force on a small area produces a large force on a large area.
- Hydraulic brakes, pneumatic jacks and a car's braking systems are application types of hydraulic systems.
Hydraulic Brakes
- Hydraulic brakes transmit force through hydraulic fluids in a system.
- This uses pistons to transmit pressure from the master cylinder through to the brake shoes.
Pressure-Force Problems
- Pascal's principle states that pressure applied to a confined fluid is transmitted equally throughout the fluid.
- Force exerted on one part of a hydraulic system can be calculated if pressure is constant and the area of another part is known.
- The pressure applied to one side of a hydraulic system is transmitted proportionally to the other side given equal cross-sectional areas.
Practice Problems
- Problems involved calculating force required to raise an object of a particular mass.
- Calculating force in a hydraulic system given dimensions by using Pascal's principle.
One for the Road
- The exerted force on a smaller piston to lift a car in a hydraulic lift.
- Calculating force in a hydraulic system given dimensions by using Pascal's principle.
Fluid Behavior and Buoyancy
- Pressure from a fluid increases with depth.
- The net upward force on an object submerged in a fluid is buoyant force.
- The buoyant force is equal to the weight of the displaced fluid.
Buoyancy
- The ability of a fluid (liquid or gas) to exert an upward force on objects immersed in it.
- Positive, Negative or Neutral Buoyancy conditions. Floating, Hovering, and Sinking of objects.
Archimedes' Principle
- Immersed partially or totally in a fluid.
- The fluid exerts an upward force on the object, which is equal to weight of the displaced fluid.
Sink or Float Problems
- Whether a substance sinks or floats depends on density and buoyancy.
- Density of object compared to density of the fluid. This condition determines whether object floats or sinks.
Why objects sink or float in fluids.
- Density and buoyancy are two factors that influence whether an object sinks or floats.
Viscosity
- A fluid's resistance to flow.
- Internal friction between fluid particles.
- High viscosity fluids such as honey flow slowly.
- Viscosity decreases with increasing temperatures and vice versus.
Bernoulli's Principle
- As the velocity of a fluid increases, the pressure exerted by the fluid decreases.
- Higher velocity equates to lower pressure in a fluid.
Fluids in Motion - The Bernoulli Effect - Applications
- The Bernoulli effect is applied to a variety of situations, including vacuum cleaners and airplane wings.
- Air moving faster over the top of an object creates a lower pressure area beneath the object.
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Description
Explore the fundamental properties of fluids, including definitions of pressure and its relationship to area. Through examples like shoes and thumb tacks, understand how pressure varies with surface area. This quiz delves into atmospheric pressure and practical applications of these concepts.