Q.1 Which of the following quantities remains constant for an incompressible fluid in steady flow?
Velocity
Pressure
Density
Temperature
Explanation - An incompressible fluid has constant density regardless of pressure or flow conditions.
Correct answer is: Density
Q.2 Pascal's principle states that a change in pressure applied to an enclosed fluid is transmitted:
Partially in the fluid
Equally in all directions
Only to the surface
Only to the bottom
Explanation - Pascal's principle asserts that any pressure change in an enclosed incompressible fluid is transmitted undiminished in all directions.
Correct answer is: Equally in all directions
Q.3 The buoyant force acting on a body submerged in a fluid is equal to:
Weight of the fluid displaced
Weight of the body
Volume of the body
Density of the fluid
Explanation - Archimedes’ principle states that the upward buoyant force equals the weight of the displaced fluid.
Correct answer is: Weight of the fluid displaced
Q.4 The SI unit of surface tension is:
N/m
N/m^2
J/m^2
Pa
Explanation - Surface tension is force per unit length along a line in the surface of a liquid, so its unit is N/m.
Correct answer is: N/m
Q.5 Which of the following statements about a real fluid is correct?
It has zero viscosity
It obeys ideal gas laws
It offers resistance to motion
Its density changes with temperature only
Explanation - A real fluid has viscosity and therefore resists relative motion between its layers.
Correct answer is: It offers resistance to motion
Q.6 The pressure at a depth h in a liquid of density ρ under gravity g is given by:
P = ρgh
P = ρg/h
P = gh/ρ
P = ρg + h
Explanation - Hydrostatic pressure in a fluid at rest is given by P = ρgh, where ρ is density, g is acceleration due to gravity, and h is depth.
Correct answer is: P = ρgh
Q.7 Which property of a liquid allows it to rise in a thin capillary tube?
Cohesion
Adhesion
Viscosity
Surface tension
Explanation - Capillary rise occurs due to adhesive forces between the liquid and the tube walls, assisted by surface tension.
Correct answer is: Adhesion
Q.8 Viscosity of a liquid is defined as:
Resistance to flow
Density per unit volume
Surface tension per unit length
Pressure at a depth
Explanation - Viscosity is a measure of internal friction or resistance to flow in a fluid.
Correct answer is: Resistance to flow
Q.9 A fluid with negligible viscosity is called:
Ideal fluid
Real fluid
Superfluid
Newtonian fluid
Explanation - An ideal fluid is incompressible and has no viscosity, thus offering no resistance to motion.
Correct answer is: Ideal fluid
Q.10 The rise or fall of a liquid in a capillary is due to:
Cohesive forces only
Adhesive forces only
Both cohesive and adhesive forces
Surface area increase
Explanation - Capillary action is due to the combined effect of cohesion (liquid-liquid attraction) and adhesion (liquid-wall attraction).
Correct answer is: Both cohesive and adhesive forces
Q.11 Bernoulli’s equation is a statement of the law of conservation of:
Mass
Energy
Momentum
Angular momentum
Explanation - Bernoulli’s principle is derived from conservation of mechanical energy for a flowing fluid.
Correct answer is: Energy
Q.12 The unit of pressure in SI system is:
Pascal
Atmosphere
Bar
Torr
Explanation - Pressure is force per unit area. The SI unit is Pascal (Pa) where 1 Pa = 1 N/m².
Correct answer is: Pascal
Q.13 A floating body displaces its own weight of the liquid. This is according to:
Pascal's law
Archimedes’ principle
Bernoulli’s theorem
Newton’s second law
Explanation - Archimedes’ principle states that a floating body displaces a weight of liquid equal to its own weight.
Correct answer is: Archimedes’ principle
Q.14 Surface tension arises due to:
Molecular attraction
Gravity
Viscosity
Pressure
Explanation - Surface tension results from cohesive forces between molecules at the surface of a liquid.
Correct answer is: Molecular attraction
Q.15 Which liquid has the highest surface tension?
Water
Mercury
Alcohol
Acetone
Explanation - Mercury has strong metallic bonding leading to the highest surface tension among common liquids.
Correct answer is: Mercury
Q.16 Poiseuille’s law is associated with:
Flow of ideal fluid
Laminar flow of viscous fluid
Turbulent flow
Surface tension
Explanation - Poiseuille’s law gives the volume flow rate of a viscous fluid through a pipe in laminar flow conditions.
Correct answer is: Laminar flow of viscous fluid
Q.17 The ratio of the buoyant force to the weight of the fluid displaced is called:
Density
Specific gravity
Relative density
Archimedes ratio
Explanation - Relative density (specific gravity) is the ratio of density of a substance to the density of a reference fluid, usually water.
Correct answer is: Relative density
Q.18 The upward force on a body immersed in a fluid is called:
Weight
Buoyant force
Drag force
Lift force
Explanation - Buoyant force is the net upward force experienced by a body submerged or partially submerged in a fluid.
Correct answer is: Buoyant force
Q.19 The phenomenon by which a liquid flows without external force through narrow spaces is called:
Capillarity
Viscosity
Diffusion
Surface tension
Explanation - Capillarity is the ability of a liquid to flow in narrow spaces against gravity due to cohesive and adhesive forces.
Correct answer is: Capillarity
Q.20 In fluids, viscosity is caused by:
Gravity
Intermolecular friction
Pressure
Temperature alone
Explanation - Viscosity arises due to internal friction between adjacent layers of fluid caused by intermolecular forces.
Correct answer is: Intermolecular friction
Q.21 A manometer is used to measure:
Flow rate
Pressure
Viscosity
Density
Explanation - A manometer is an instrument that measures fluid pressure by balancing it against a column of liquid.
Correct answer is: Pressure
Q.22 The angle of contact in a liquid-solid system depends on:
Surface tension only
Cohesive and adhesive forces
Viscosity
Density
Explanation - The angle of contact is determined by the balance between cohesive forces within the liquid and adhesive forces between the liquid and solid.
Correct answer is: Cohesive and adhesive forces
Q.23 The pressure difference across a curved liquid surface is given by:
ΔP = 2T/r
ΔP = T/r^2
ΔP = ρgh
ΔP = μv/r
Explanation - For a spherical liquid surface, the pressure difference between inside and outside is ΔP = 2T/r, where T is surface tension and r is radius of curvature.
Correct answer is: ΔP = 2T/r
Q.24 The SI unit of viscosity is:
Pa·s
N/m
kg/m^3
N/m^2
Explanation - Dynamic viscosity has SI unit Pascal-second (Pa·s), which is equivalent to N·s/m².
Correct answer is: Pa·s
Q.25 Which of the following fluids can be considered ideal?
Water at room temperature
Air at standard conditions
A superfluid
Mercury at room temperature
Explanation - A superfluid, like liquid helium at very low temperature, has negligible viscosity and can be approximated as an ideal fluid.
Correct answer is: A superfluid