Physics

Fluid Mechanics

637 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
  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement 'a' is a false statement. Thus, it is the correct option. The pressure exerted by a liquid increases with the increase in depth inside the liquid.

Multiple choice
  1. gravitational force

  2. adhesion

  3. surface tension

  4. atmospheric pressure

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Surface tension is the cohesive force between liquid molecules that causes water droplets to minimize their surface area. A sphere has the minimum surface area for a given volume, which is why small water droplets naturally form spherical shapes.

Multiple choice
  1. y

  2. p + WP

  3. p + TP

  4. ys + yp

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Water potential (Ψ) is the sum of its components. In plant physiology, Ψ = Ψs + Ψp, where Ψs (or yw) is solute potential (osmotic potential) and Ψp (or yp) is pressure potential (turgor pressure). Option D shows this relationship correctly (ys + yp, using subscripts for solute and pressure). Options A, B, and C are incorrect representations of the water potential equation.

Multiple choice
  1. atmospheric pressure

  2. water pressure

  3. buoyant force

  4. none

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Bar is a metric unit of pressure equal to 100,000 Pa (pascals). It is commonly used to express atmospheric pressure, where 1 bar is approximately equal to Earth's atmospheric pressure at sea level. It is not specifically for water pressure or buoyant force, though it can measure any pressure.

Multiple choice
  1. atmospheric pressure

  2. gravitational force

  3. surface tension

  4. capillary rice

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Surface tension minimizes the surface area of a liquid for a given volume, causing water droplets to become spherical (a sphere has minimum surface area). Atmospheric pressure and gravitational force act externally, while 'capillary rice' is a typo for 'capillary rise' (a different phenomenon).

Multiple choice
  1. 00 C

  2. 40 C

  3. 1000 C

  4. 100 C

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water reaches its maximum density at approximately 4°C (39°F). This unusual property occurs because water molecules form a highly ordered structure as temperature decreases from 4°C to 0°C, causing expansion. This property is crucial for aquatic life as ice floats, insulating the water below and allowing organisms to survive under frozen surfaces.

Multiple choice
  1. Surface tension of water is more than that of ice.

  2. Density of water is more than ice.

  3. Mass of ice is more than that of water.

  4. Density of ice is more than that of water.

  5. Surface tension of ice is more than that of water.

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct option. Ice floats because it is about 9% less dense than liquid water. In other words, ice takes up about 9% more space than water. The heavier water displaces the lighter ice, so ice floats to the top.  

Multiple choice
  1. 1 and 2 only

  2. 2 and 3 only

  3. 1 and 3 only

  4. 1, 2 and 3

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Archimedes' principle, the fraction of a floating object submerged depends on the ratio of the object's density to the liquid's density. The mass of the ball is irrelevant - only the densities matter. For a given liquid density, balls with the same density will float at the same level regardless of mass.

Multiple choice
  1. capillary action of water

  2. Pascal's law

  3. Archimedes principle

  4. surface tension of water

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Archimedes' principle, an object immersed in a fluid experiences an upward buoyant force equal to the weight of the displaced fluid. When the jug is in the bucket of water, the buoyant force reduces its apparent weight. When removed from water, this force disappears and the full weight is felt.

Multiple choice
  1. 1%

  2. 11%

  3. 21%

  4. 75%

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a floating body, the fraction submerged equals the ratio of densities: fraction_submerged = density_iceberg / density_water. Here: 0.93/1.03 = 0.9029, meaning about 90.29% is submerged. The visible (above water) fraction is 1 - 0.9029 = 0.0971 or 9.71%, which rounds to approximately 11%. Option B is closest.

Multiple choice
  1. Oil is lighter than water

  2. Oil is more viscous

  3. Oil does not mix with water

  4. Surface tension of oil is much smaller that of water

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oil spreads on water because water's high surface tension creates a strong 'skin' effect. Oil has much lower surface tension, allowing it to form a thin film across the water surface. Density (option A) and viscosity (option B) are secondary factors.

Multiple choice
  1. near the bottom of the bottle

  2. in the middle of the bottle

  3. near the neck of the bottle

  4. uniformly all over the bottle

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the bottle is swung, the liquid is pushed outward by centrifugal force. The air bubbles, being less dense than the liquid, are displaced toward the region of lower pressure, which is the center of rotation (the neck).

Multiple choice
  1. weight in water

  2. volume

  3. weight in air

  4. density

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Archimedes' principle, the weight lost by an object immersed in a fluid is equal to the weight of the fluid displaced. If the weight lost is the same, the volume of fluid displaced must be the same, which implies the objects have the same volume.