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 physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

What happens when an object having density less than that of water is immersed in it?

  1. It sinks

  2. It floats

  3. Unsure

  4. May sink or float
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

the buoyant force depends on the density of liquid. When the density of the object is less than that of the liquid, it floats on the liquid because the upthrust or buoyant force of water is more than the gravity acting on the object.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

If the weight of the body immersed in the liquid is equal to the force of buoyancy acting on it, then the body will

  1. Float above the liquid surface

  2. Float just inside the liquid surface.

  3. Sink

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If the weight of the body immersed in the liquid is equal to the force of buoyancy acting on it, then the body will float just inside the liquid surface.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A ball rise with constant velocity, to the surface of a liquid whose density is four times that of the ball. The ratio of the v force to weight of the ball is

  1. 1

  2. 2

  3. 3

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

For a body rising with constant velocity, the forces are balanced: Buoyancy = Weight + Viscous Force. F_b = rho_liquid * V * g = 4 * rho_ball * V * g = 4 * Weight. Therefore, Viscous Force = F_b - Weight = 4W - W = 3W. The ratio of viscous force to weight is 3.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A body is float inside liquid. If we increase temperature then what charges occur in buoyancy force?(Assume body is always in floating condition )

  1. Buoyancy force will condition

  2. Buoyancy force will increase

  3. Buoyancy force remains constant

  4. Cannot be calculated from given statement
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A wooden cube floats just inside the water, when a mass of $x$ (in grams) is placed on it. If the mass is removed, the cube floats with a height $\dfrac{x}{100}\ cm$ above the water surface. The length of the side of cube is (density of water is $1000\ kg/m^{3}$)

  1. $10\ cm$
  2. $15\ cm$
  3. $20\ cm$
  4. $30\ cm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

Consider a small balloon filled with an ideal gas which is submerged in water. Assuming that the temperature is the same everywhere in the water, the buoyant force on the balloon when it is at a depth d below the surface, in terms of its volume at the surface $V _ { 0 }$ , the atmospheric pressure $P _ { 0 }$ , the density of water $\rho _ { 0 }$ , and the acceleration due to gravity g.

  1. $F _ { B } = \frac { P _ { 0 } V _ { 0 } } { d + \frac { P _ { 0 } } { \rho g } }$
  2. $F _ { B } = \frac { P _ { 0 } V _ { 0 } } { d \rho g + P _ { 0 } }$
  3. $F _ { B } = \frac { d \rho g + P _ { 0 } } { P _ { 0 } V _ { 0 } }$
  4. $F _ { B } = \frac { P _ { 0 } V _ { 0 } } { d + \frac { \rho g } { P _ { 0 } } }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A body is floating in water with $80$% of its volume below the surface of water. What is the density of body?

  1. $666.7kg/{ m }^{ 3 }$
  2. $777.6kg/{ m }^{ 3 }$
  3. $800kg/{ m }^{ 3 }$
  4. $876.6kg/{ m }^{ 3 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a floating body, the fraction submerged is equal to the ratio of densities. 0.80 = rho_body / rho_water. rho_body = 0.80 * 1000 kg/m^3 = 800 kg/m^3.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A boat is floating in water at $0^{ \circ  }C$ such that 97% of the volume of the boat is submerged in water . The temperature at which the boat will just completely sink in water is $(\gamma _{ R }=3\times { 10 }^{ -4 }/{ ^{ 0 }C })(nearly)$ 

  1. ${ 100 }{ ^{ 0 }C }$
  2. ${ 103 }{ ^{ 0 }C }$
  3. ${ 60 }{ ^{ 0 }C }$
  4. ${ 50 }{ ^{ 0 }C }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The boat sinks when the volume of water displaced equals the volume of the boat. Using the thermal expansion formula V = V0(1 + gamma*deltaT), we set the submerged volume to 100% (1.0) and solve for deltaT given the initial 97% (0.97) submerged volume at 0 degrees Celsius.