A wire elongates by ΔL when loaded. The proportional constant linking stress and strain is:
A Bulk modulus
B Young’s modulus
C Shear modulus
D Breaking stress
Young’s modulus = stress/strain for tensile deformation.
Elastic limit represents:
A Permanent deformation starts
B Ultimate strength
C Maximum elastic energy
D Zero deformation
After elastic limit, deformation becomes irreversible.
A material with Poisson’s ratio 0.5 is:
A Perfectly plastic
B Incompressible
C Brittle
D Highly ductile
For incompressible materials, Poisson’s ratio ≈ 0.5.
The dimension of stress is same as:
A Energy
B Pressure
C Force
D Strain
Stress = force/area → units identical to pressure.
The slope of stress–strain curve in elastic region equals:
A Shear modulus
B Breaking stress
C Young’s modulus
D Elastic limit
The slope is E = stress/strain.
A ductile material must have:
A Very large breaking stress
B Very large plastic region
C Very low Young’s modulus
D No yield point
Ductile materials show long plastic deformation before breaking.
Shear strain is measured in:
A Radians
B Joules
C Newtons
D Meters
Shear strain is angular deformation → radian (dimensionless).
Spring constant k depends on:
A Material only
B Shape only
C Material and dimensions
D Mass suspended
k depends on material modulus and spring geometry.
Work done in stretching a wire to extension x is:
A kx
B kx²
C ½kx²
D 2kx
Elastic energy stored = ½kx².
A perfectly elastic body has:
A Plastic deformation
B No deformation
C Complete recovery
D Zero Young’s modulus
Perfectly elastic bodies regain full shape after load removal.
Pressure at a point in fluid is:
A Greater sideways
B Greater downward
C Same in all directions
D Zero
Pascal’s law → pressure is isotropic in static fluid.
The relation between speed and pressure in fluid flow is explained by:
A Archimedes’ law
B Stokes’ law
C Bernoulli’s equation
D Continuity equation
Bernoulli: high speed → low pressure.
A body fully immersed experiences:
A Buoyant force equal to its weight
B Buoyant force equal to displaced fluid weight
C No buoyant force
D Buoyant force equal to density
Archimedes’ principle.
Laminar flow is characterised by:
A Irregular paths
B Streamlines
C Turbulence
D Shock waves
Smooth, parallel streamlines identify laminar flow.
Torricelli’s law describes:
A Velocity of efflux
B Terminal velocity
C Drag force
D Capillary rise
v = √(2gh) for fluid exiting an orifice.
Fluid density increases:
A With altitude
B With temperature
C With pressure
D In vacuum
Increased pressure compresses fluid slightly → density increases.
A hydraulic press multiplies:
A Pressure
B Energy
C Work
D Force
Pascal’s principle allows force multiplication.
Flow rate increases when:
A Pipe is longer
B Pipe is narrower
C Pressure difference increases
D Temperature decreases
Greater pressure difference → higher flow.
Viscous drag depends on:
A Surface area and velocity
B Pressure
C Temperature only
D Density only
For Stokes law fluids, F ∝ r × v.
The SI unit of buoyant force is:
A Pascal
B Joule
C Newton
D Watt
Buoyant force is simply a force measured in Newtons.
Viscosity of a fluid refers to:
A Friction between fluid layers
B Density variation
C Elasticity of fluid
D Pressure difference
Viscosity describes internal friction in fluid layers.
Surface tension is caused by:
A Adhesion
B Cohesion
C Evaporation
D Pressure difference
Cohesive forces at the surface create tension.
A liquid rises in a capillary tube when:
A γ < 0
B Adhesive forces > cohesive forces
C Density is high
D Temperature is high
Strong adhesion pulls liquid upward.
Temperature affects viscosity of liquids by:
A Increasing it
B Decreasing it
C Keeping it same
D Making it zero
Liquids become less viscous when heated.
With increasing temperature, surface tension:
A Increases
B Decreases
C Becomes zero
D Remains constant
High temperature interferes with cohesive forces.
Drops of water are spherical because:
A Density
B Gravity
C Viscosity
D Surface tension
Surface tension tries to minimise surface area → sphere.
Terminal velocity occurs when:
A Net force = 0
B Buoyant force = 0
C Velocity is infinite
D Weight becomes zero
Forces balance → constant velocity.
Reynolds number determines:
A Elasticity
B Turbulence
C Heat capacity
D Density
Higher Reynolds number → turbulent flow.
Wetting of surfaces depends on:
A Contact angle
B Thermal conductivity
C Viscosity
D Density
Lower contact angle → better wetting.
Capillary depression occurs when:
A Adhesion > cohesion
B Cohesion > adhesion
C Density is low
D Tube radius is large
Strong cohesion pulls liquid downward (e.g., mercury).
Heat transfer without medium is:
A Conduction
B Convection
C Radiation
D Evaporation
Radiation requires no material medium.
Temperature is measured using:
A Pascal’s law
B Zeroth law
C First law
D Boyle’s law
Zeroth law defines thermal equilibrium → basis of thermometry.
When a solid is heated, it expands because:
A Mass increases
B Molecular spacing increases
C Molecules break
D Density increases
Vibrations increase, increasing average separation.
Specific heat is highest for:
A Metals
B Water
C Air
D Glass
Water has very high heat capacity.
Latent heat is energy absorbed during:
A Cooling
B Heating
C Temperature change
D Phase change
Latent heat changes phase without temperature change.
Metals feel colder than wood because:
A Metals have higher density
B Metals are better conductors
C Metals reflect light
D Metals have high emissivity
Faster heat conduction makes metals seem colder.
In thermal equilibrium:
A No heat exchange
B Pressure fixed
C Volume constant
D Temperature varies
Bodies in equilibrium exchange no net heat.
Water expands when cooled below:
A 10°C
B 8°C
C 4°C
D 0°C
Anomalous expansion of water.
Conduction requires:
A Free electrons
B Fluid motion
C Vacuum
D No medium
Free electrons in metals enhance conduction.
A black body is a:
A Perfect absorber
B Perfect reflector
C Polished surface
D Transparent object
Black bodies absorb all incident radiation.
The equation PV = constant holds for:
A Isothermal process
B Adiabatic process
C Isochoric process
D Isobaric process
Boyle’s law applies at constant temperature.
RMS speed depends on:
A Mass of gas
B Temperature
C Both A and B
D Neither
vrms = √(3RT/M).
Gas pressure is due to:
A Attraction between molecules
B Repulsion
C Wall collisions
D Viscosity
Molecule-wall collisions create pressure.
For ideal gas, internal energy depends on:
A Pressure
B Volume
C Temperature
D Density
U ∝ T for ideal gas.
Mean free path increases when:
A Number density increases
B Pressure increases
C Temperature increases
D Volume decreases
Higher temperature → faster motion → fewer effective collisions.
First law of thermodynamics is:
A Q = W
B ΔQ = ΔU + W
C W = 0
D ΔU = 0
This expresses energy conservation for thermodynamic systems.
For isothermal expansion of an ideal gas:
A Temperature increases
B Internal energy increases
C Internal energy stays constant
D Pressure constant
U depends only on T; if T constant, U constant.
In cyclic process, ΔU =
A Maximum
B Minimum
C Zero
D Infinite
Internal energy is a state function → returns to initial value.
Efficiency of heat engine cannot exceed:
A 0%
B 50%
C Carnot efficiency
D 100%
Carnot sets theoretical upper limit.
Entropy of an isolated system:
A Always increases
B Always decreases
C Remains constant
D Decreases then increases
Second law: entropy of isolated system never decreases.