Physics

Fluid Mechanics

673 Questions

Fluid mechanics is a core physics topic that evaluates the principles of liquid pressure, buoyancy, density, and viscosity through complex numerical problems. The questions require calculating the volume of submerged objects, understanding hydraulic jumps, and applying fundamental fluid statics principles. It is a highly scoring subject for candidates preparing for technical and engineering competitive exams.

Liquid pressure and depthBuoyancy and densityVolume expansionHydraulic jump calculationsSurface tension mechanics

Fluid Mechanics Questions

Multiple choice

What is the equation for calculating the buoyant force acting on an object submerged in a fluid?

  1. F_b = ρVg

  2. F_b = ρgh

  3. F_b = mg

  4. F_b = Vg
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The buoyant force acting on an object submerged in a fluid is given by the equation F_b = ρVg, where F_b is the buoyant force, ρ is the fluid density, V is the volume of the object submerged in the fluid, and g is acceleration due to gravity.

Multiple choice

What is the pressure at the bottom of a container filled with a liquid?

  1. Zero

  2. Equal to atmospheric pressure

  3. Equal to the weight of the liquid

  4. Equal to the weight of the liquid divided by the surface area of the container
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pressure at the bottom of a container filled with a liquid is equal to the weight of the liquid divided by the surface area of the container. This pressure is known as hydrostatic pressure.

Multiple choice

What is the relationship between pressure and height in a liquid?

  1. Pressure is directly proportional to height

  2. Pressure is inversely proportional to height

  3. Pressure is independent of height

  4. Pressure varies randomly with height
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a liquid, pressure increases linearly with height. This relationship is known as hydrostatic pressure, and it is expressed by the equation P = ρgh, where P is pressure, ρ is fluid density, g is acceleration due to gravity, and h is height.

Multiple choice

What is the principle of communicating vessels?

  1. Liquids in communicating vessels will always reach the same level

  2. Liquids in communicating vessels will always reach different levels

  3. Liquids in communicating vessels will reach the same level only if they have the same density

  4. Liquids in communicating vessels will reach the same level only if they have the same temperature
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The principle of communicating vessels states that liquids in communicating vessels will always reach the same level, regardless of their shape or size. This principle is a consequence of Pascal's Law and the fact that liquids seek their own level.

Multiple choice

What is the relationship between the specific gravity of a fluid and its density?

  1. Specific gravity is equal to density

  2. Specific gravity is inversely proportional to density

  3. Specific gravity is independent of density

  4. Specific gravity varies randomly with density
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Specific gravity is defined as the ratio of the density of a substance to the density of water at 4°C. Since the density of water at 4°C is 1000 kg/m^3, the specific gravity of a substance is numerically equal to its density in kg/m^3.

Multiple choice

What is the relationship between the buoyant force acting on an object and the object's density?

  1. Buoyant force is directly proportional to the object's density

  2. Buoyant force is inversely proportional to the object's density

  3. Buoyant force is independent of the object's density

  4. Buoyant force varies randomly with the object's density
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The buoyant force acting on an object is directly proportional to the object's density. This relationship is expressed by the equation F_b = ρVg, where F_b is the buoyant force, ρ is the fluid density, V is the volume of the object submerged in the fluid, and g is acceleration due to gravity.

Multiple choice

What is the primary cause of lift in a fluid?

  1. Pressure difference

  2. Viscosity

  3. Gravity

  4. Surface roughness
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lift in a fluid is primarily caused by the pressure difference between the upper and lower surfaces of an object moving through the fluid.

Multiple choice

What is the relationship between drag force and the density of the fluid?

  1. Linear

  2. Exponential

  3. Quadratic

  4. Inversely proportional
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Drag force is proportional to the density of the fluid.

Multiple choice

What is the term used to describe the phenomenon where a fluid flows smoothly over a surface?

  1. Laminar flow

  2. Turbulent flow

  3. Boundary layer

  4. Drag crisis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Laminar flow is the term used to describe the phenomenon where a fluid flows smoothly over a surface.

Multiple choice

What are the main causes of cavitation?

  1. High fluid velocity

  2. Low fluid pressure

  3. High fluid temperature

  4. Low fluid temperature
Reveal answer Fill a bubble to check yourself
Correct answer
Explanation

Cavitation is primarily caused by a combination of high fluid velocity and low fluid pressure. When the fluid velocity is high, it creates a region of low pressure, which can cause the liquid to vaporize and form vapor bubbles.

Multiple choice

What is the cavitation number?

  1. The ratio of the NPSH to the dynamic head of the pump

  2. The ratio of the vapor pressure of the liquid to the dynamic head of the pump

  3. The ratio of the NPSH to the static head of the pump

  4. The ratio of the vapor pressure of the liquid to the static head of the pump
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The cavitation number is the ratio of the NPSH to the dynamic head of the pump. It is a dimensionless number that is used to predict the likelihood of cavitation in a pump.

Multiple choice

What is the effect of fluid elasticity on cavitation?

  1. Increasing the fluid elasticity increases the likelihood of cavitation

  2. Increasing the fluid elasticity decreases the likelihood of cavitation

  3. Fluid elasticity has no effect on cavitation

  4. The effect of fluid elasticity on cavitation is not well-defined
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Increasing the fluid elasticity decreases the likelihood of cavitation because it makes it more difficult for vapor bubbles to grow and collapse. Elastic fluids have the ability to store energy, which can be used to absorb the energy of the collapsing vapor bubbles. This reduces the damage caused by cavitation and makes it less likely to occur.

Multiple choice

Which fluid property is important in determining the buoyancy of an object?

  1. Density

  2. Viscosity

  3. Surface Tension

  4. Compressibility
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Density is the key fluid property that determines the buoyancy of an object. Buoyancy is the upward force exerted by a fluid on an object immersed in it.

Multiple choice

The compressibility of a fluid is inversely proportional to:

  1. Density

  2. Viscosity

  3. Surface Tension

  4. Bulk Modulus
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Compressibility is the reciprocal of the bulk modulus. Therefore, it is inversely proportional to the bulk modulus.

Multiple choice

What are the main challenges in offshore engineering hydrodynamics?

  1. The complex and dynamic nature of the marine environment

  2. The need to design and analyze offshore structures that are safe and reliable

  3. The need to minimize the environmental impact of offshore activities

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The main challenges in offshore engineering hydrodynamics include the complex and dynamic nature of the marine environment, the need to design and analyze offshore structures that are safe and reliable, and the need to minimize the environmental impact of offshore activities.