Examkin

Properties of Fluids

7 soru

Tüm türler7Çoktan seçmeli4Sayısal1Eşleştirme1Sıralama1
Soru 1Soru →

A heavy-duty hydraulic press is designed to operate using hydraulic oil with a specific gravity of 0.85. During maintenance, a large volume of air is accidentally trapped in the sealed main pressure line. When the pump applies 2,000 psi of pressure to the system, which of the following best describes how the properties of the contents will affect the machine's operation?

Cevabı ve açıklamayı göster

Cevap: The trapped air will compress significantly before the oil can transmit full force, causing a delayed and spongy cylinder response.

Cevap

The trapped air will compress significantly before the oil can transmit full force, causing a delayed and spongy cylinder response.
Hydraulic systems rely on the incompressibility of liquids to transmit force instantaneously and efficiently. When air (a gas) enters the system, it acts like a weak mechanical spring because gases are highly compressible. The pump's applied pressure will first crush the air pocket into a smaller volume before enough pressure builds up to move the heavy cylinder, resulting in a delayed, inefficient, and spongy mechanical action.

Adım Adım Çözüm

1
Identify the two different fluids in the closed hydraulic system.
The system contains a liquid (hydraulic oil) and a gas (air).
Different phases of matter respond completely differently to applied pressure.
2
Evaluate the compressibility of each fluid.
Liquids are nearly incompressible, meaning their volume remains virtually constant under high pressure. Gases are highly compressible, meaning their volume decreases significantly when pressure is applied.
Understanding compressibility is essential to predicting the physical behavior of the system.
3
Determine the mechanical effect on the hydraulic press.
When the 2,000 psi is applied, the work energy initially goes into compressing the trapped air pocket rather than moving the cylinder. This creates a delay and a soft, 'spongy' feel until the air is fully compressed.
Force cannot be efficiently transmitted through a fluid medium until all highly compressible elements in the line are reduced in volume.

Anahtar Kavram

Fluid Compressibility
Tahmini Süre:1m 0s
Soru 2Soru →

In a mechanical workshop, two identical syringes are sealed at the tip. One syringe is filled with atmospheric gas, and the other is filled with brake fluid. When a mechanic pushes down hard on both plungers, what physical difference between the two substances becomes obvious?

Cevabı ve açıklamayı göster

Cevap: The gas volume decreases greatly, while the liquid volume stays nearly constant.

Cevap

The gas volume decreases greatly, while the liquid volume stays nearly constant.
Gases have widely spaced molecules and are highly compressible, meaning their volume decreases visibly under pressure. Liquids have closely packed molecules and are virtually incompressible, so their volume remains almost entirely constant even when force is applied.

Adım Adım Çözüm

1
Identify the states of matter for the substances in the syringes.
The atmospheric gas is in a gaseous state, and the brake fluid is in a liquid state.
Determining the state of matter is the first step in predicting physical behavior under pressure.
2
Recall the compressibility properties of gases versus liquids.
Gases are highly compressible because their molecules are far apart. Liquids are generally considered incompressible because their molecules are closely packed.
This fundamental principle dictates how each fluid phase reacts to an applied force.
3
Apply this principle to the scenario of pushing the plungers.
The force easily compresses the gas, allowing its plunger to move down significantly. The force cannot significantly compress the liquid, so its plunger barely moves.
The physical difference in molecular spacing results in a highly visible difference in volume change.

Anahtar Kavram

Compressibility differences between fluid phases
Soru 3Soru →

Match each physical property of a fluid to its correct definition.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Density
Specific Gravity
Viscosity
Compressibility

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

Density matches 'The mass of a fluid per unit of its volume.' Specific Gravity matches 'The ratio of a fluid's density compared to the density of pure water.' Viscosity matches 'A fluid's internal resistance to flowing.' Compressibility matches 'The measure of a fluid's volume decrease when placed under pressure.'
Each fluid property has a distinct operational definition in mechanical systems: density is mass over volume, specific gravity compares that density to water, viscosity measures flow resistance, and compressibility measures volume change under pressure.

Adım Adım Çözüm

1
Identify the definition of density.
Density is mapped to mass per unit volume.
This is a fundamental physical property of all matter that determines its weight for a given size.
2
Identify the definition of specific gravity.
Specific gravity is mapped to the ratio of a fluid's density to water.
It acts as a unitless multiplier comparing a fluid to a standard baseline.
3
Identify the definition of viscosity.
Viscosity is mapped to internal resistance to flow.
It dictates how easily fluids move through mechanical components like pipes and engines.
4
Identify the definition of compressibility.
Compressibility is mapped to how much volume decreases under pressure.
This property separates liquids (nearly incompressible) from gases (highly compressible) in hydraulic and pneumatic systems.

Anahtar Kavram

Foundational fluid properties determine how fluids behave and function in mechanical, hydraulic, and pneumatic applications.
Tahmini Süre:45s
Soru 4Soru →

A mechanic pours four common automotive fluids into a clear, tall recovery cylinder. Assuming they do not mix and are allowed to settle completely into distinct layers, arrange the fluids in order from the TOP layer to the BOTTOM layer.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct order from the top layer to the bottom layer is: Gasoline, SAE 30 Engine Oil, Fresh Water, and finally Ethylene Glycol (Antifreeze).
When immiscible fluids are mixed and allowed to settle, they separate into distinct layers based on their specific gravity. The fluid with the lowest specific gravity (gasoline, ~0.73) will float on top. Engine oil (~0.88) comes next, floating on the fresh water (1.0). Ethylene glycol antifreeze (~1.11) is the densest fluid of the group and will sink to the very bottom.

Adım Adım Çözüm

1
Identify the physical property that determines how fluids layer.
Fluids layer based on their density or specific gravity. The least dense fluid floats on top, and the most dense fluid sinks to the bottom.
Buoyancy dictates that lighter fluids will displace heavier ones downwards.
2
Recall the relative specific gravities of the listed automotive fluids.
Gasoline is the lightest (SG ~0.73), followed by engine oil (SG ~0.88), fresh water (SG 1.0), and ethylene glycol antifreeze (SG ~1.11).
Understanding the density of common mechanical fluids is necessary for diagnosing leaks and fluid separation.
3
Arrange the fluids according to their specific gravity from lowest (top) to highest (bottom).
Gasoline, Engine Oil, Water, Antifreeze.
This matches the instruction to order from the top layer to the bottom layer.

Anahtar Kavram

Density and Specific Gravity
Soru 5Soru →

A hydraulic accumulator is a sealed, rigid tank that contains both hydraulic fluid (a liquid) and pressurized nitrogen (a gas). When a pump forces additional hydraulic fluid into the tank and significantly raises the internal pressure, which of the following best describes the volumetric changes of the original contents?

Cevabı ve açıklamayı göster

Cevap: The volume of the nitrogen gas decreases significantly, while the volume of the original hydraulic fluid remains virtually unchanged.

Cevap

The volume of the nitrogen gas decreases significantly, while the volume of the original hydraulic fluid remains virtually unchanged.
Liquids, such as hydraulic fluid, are practically incompressible, meaning their volume does not significantly change when subjected to high pressure. Gases, such as nitrogen, are highly compressible. When the pump forces more liquid into the rigid tank, the internal pressure rises. The gas acts like a spring, compressing into a smaller volume to accommodate the new liquid, while the original liquid retains its volume.

Adım Adım Çözüm

1
Identify the states of matter of the materials inside the accumulator.
The nitrogen is a gas, and the hydraulic fluid is a liquid.
Different states of matter respond differently to applied pressure.
2
Recall the compressibility property of liquids.
Liquids are practically incompressible.
This means adding pressure will not noticeably change the volume of the original hydraulic fluid.
3
Recall the compressibility property of gases.
Gases are highly compressible.
This means the nitrogen gas will be forced into a smaller volume as the pressure inside the rigid tank increases.
4
Combine these principles to determine the outcome.
The added fluid forces the gas to compress into a smaller space, while the original liquid maintains its volume.
This allows the rigid tank to accommodate the additional hydraulic fluid.

Anahtar Kavram

Compressibility of Liquids vs. Gases
Tahmini Süre:1m 0s
Soru 6Soru →

A marine engineer is filling a sealed buoyancy tank with a specialized flotation fluid. The system requires a fluid with a specific gravity of 0.850.85 to provide the correct lift. If the internal volume of the tank is 0.4 m30.4 \text{ m}^3, what must the total mass of the fluid be? (Assume the density of water is 1000 kg/m31000 \text{ kg/m}^3)

Cevabı ve açıklamayı göster

Cevap: 340

Cevap

The correct mass is 340 kg340 \text{ kg}.
The correct answer is found by first converting the unitless specific gravity into an actual density by multiplying it by the density of water (0.85×1000=850 kg/m30.85 \times 1000 = 850 \text{ kg/m}^3). The total mass is then calculated by multiplying this density by the given volume (850×0.4=340 kg850 \times 0.4 = 340 \text{ kg}).

Adım Adım Çözüm

1
Calculate the density of the fluid using its specific gravity.
Density = 850 kg/m3850 \text{ kg/m}^3
Specific gravity is defined as the ratio of a fluid's density to the density of water (1000 kg/m31000 \text{ kg/m}^3). Therefore, density equals 0.85×10000.85 \times 1000.
2
Calculate the mass of the fluid using its density and volume.
Mass = 340 kg340 \text{ kg}
Mass is the product of density and volume. 850 kg/m3×0.4 m3=340 kg850 \text{ kg/m}^3 \times 0.4 \text{ m}^3 = 340 \text{ kg}.

Anahtar Kavram

The relationship between specific gravity, density, and volume to determine the mass of a fluid.
Soru 7Soru →

An outdoor hydraulic lift operates noticeably slower and requires more effort from the pump on a freezing winter morning compared to a hot summer afternoon. Assuming the mechanical components are functioning normally, which of the following fluid properties best explains this sluggish performance?

Cevabı ve açıklamayı göster

Cevap: The viscosity of the hydraulic fluid increases in cold temperatures, creating greater internal resistance to flow.

Cevap

The viscosity of the hydraulic fluid increases in cold temperatures, creating greater internal resistance to flow.
Viscosity measures a fluid's internal resistance to flow. In virtually all lubricating and hydraulic liquids, viscosity increases as the temperature drops, causing the fluid to become thicker. This increased thickness creates drag inside the hydraulic lines and valves, resulting in slower mechanical operation.

Adım Adım Çözüm

1
Analyze the mechanical symptom described in the scenario.
The hydraulic lift is operating slowly (sluggishly) in cold temperatures.
Identifying the symptom helps isolate which physical property of the fluid is changing with the temperature drop.
2
Evaluate how temperature affects the physical properties of liquids.
As temperature decreases, the internal friction of a liquid increases.
Understanding the inverse relationship between temperature and liquid viscosity is a core concept in mechanical fluid maintenance.
3
Connect the changing fluid property to the mechanical outcome.
Higher internal friction (higher viscosity) means the fluid resists flowing through hoses and valves, slowing down the machine's operation.
This confirms that increased viscosity is the direct cause of the sluggish mechanical performance.

Anahtar Kavram

Viscosity and Temperature Relationship
Tahmini Süre:45s
Properties of Fluids Alıştırma Soruları — Armed Services Vocational Aptitude Battery (ASVAB) | Examkin