If the length of a wire is doubled while radius remains same, its extension under same load will:
A Reduce to half
B Remain same
C Double
D Become four times
Extension ∝ length (ΔL ∝ L).
A material with high modulus of elasticity is:
A Easily stretchable
B Very rigid
C Highly plastic
D Very soft
Higher modulus → higher rigidity.
Stress corresponding to permanent deformation beginning is:
A Elastic limit
B Breaking stress
C Yield stress
D Ultimate stress
Yield point marks start of plastic deformation.
Strain is:
A Force
B Work
C Dimensionless
D Pressure
Strain = ΔL/L → dimensionless quantity.
A thin wire breaks more easily because:
A Less Young’s modulus
B Higher stress for same force
C Lower strain
D Higher density
Stress = force / area → smaller area → higher stress.
Young’s modulus relates to:
A Volume change
B Shearing deformation
C Linear deformation
D Plastic limit
Young’s modulus applies to tensile/longitudinal deformation.
A material with low Poisson ratio:
A Contracts little laterally
B Contracts a lot
C Is brittle
D Is perfectly elastic
Low ν means very small lateral contraction for given extension.
Breaking stress depends on:
A Length
B Material
C Area
D Temperature only
Breaking stress is a material property, independent of dimensions.
A spring in parallel combination has effective spring constant:
A k₁ + k₂
B (k₁k₂)/(k₁ + k₂)
C k₁ − k₂
D k₁/k₂
Parallel springs add stiffness: k_eq = k₁ + k₂.
Area under load–extension graph gives:
A Momentum
B Work done
C Stress
D Strain
Area = force × extension = work.
Pascal’s law states:
A Pressure at depth depends on shape
B Pressure is transmitted equally in all directions
C Pressure is zero at bottom
D Fluids do not exert pressure
Pascal’s law governs hydraulic systems.
Archimedes’ principle applies to:
A Solids only
B Gases only
C Liquids only
D Both liquids and gases
Buoyant force acts in any fluid (liquid or gas).
When fluid velocity increases, pressure:
A Increases
B Decreases
C Remains constant
D Becomes zero
Bernoulli’s principle.
Streamline flow occurs when:
A Reynolds number < 2000
B Reynolds number > 5000
C Velocity very high
D Pressure zero
Laminar flow for low Reynolds number.
Drag force for a sphere in Stokes’ region is proportional to:
A v²
B v
C 1/v
D v³
Stokes’ drag F = 6π η r v.
In a Venturi meter, fluid speed increases in:
A Wide section
B Narrow section
C Everywhere
D Only at inlet
According to continuity equation.
Pressure difference needed to support a column of height h is:
A h
B ρh
C ρgh
D gh
Hydrostatic pressure.
Density of fluid determines:
A Buoyant force
B Surface tension
C Temperature
D Compressibility
Greater density → greater buoyant force.
A floating body displaces fluid equal to its:
A Mass
B Volume
C Weight
D Density
Buoyant force = weight of displaced fluid = object’s weight.
Fluid with constant density is called:
A Ideal fluid
B Newtonian fluid
C Incompressible fluid
D Perfect gas
Incompressible means density doesn’t change significantly.
Viscosity of gases increases because:
A Temperature reduces energy
B Collisions increase momentum transfer
C Density increases
D Pressure decreases
Gas viscosity arises from molecular collisions which increase with temperature.
Surface energy per unit area equals:
A Viscosity
B Work function
C Surface tension
D Elastic modulus
Surface tension equals energy required to increase area by unit amount.
Capillary rise formula includes:
A Radius squared
B Inverse radius
C Density only
D Area only
h ∝ 1/r.
A liquid wets glass when:
A Cohesion > adhesion
B Adhesion > cohesion
C Contact angle = 90°
D Surface tension infinite
Adhesive forces pull the liquid along the surface.
Surface tension acts:
A Downward
B Upward
C Tangential to surface
D Radially outward
Surface tension acts along the surface boundary.
Terminal velocity increases with:
A Decreasing radius
B Increasing viscosity
C Decreasing density difference
D Increasing radius
vₜ ∝ r² (Stokes region).
Capillary rise is independent of:
A Tube radius
B Surface tension
C Nature of liquid
D Tube length beyond liquid level
Only radius, density, and surface tension matter.
A soap bubble has two surfaces. Its excess pressure is:
A 2T/r
B T/r
C 4T/r
D T/2r
Excess pressure = 4T/r for soap bubble (two surfaces).
A mercury drop is spherical more strongly than a water drop because:
A Less density
B More viscosity
C Very high surface tension
D High vapor pressure
Mercury has much higher surface tension → well-defined sphere.
Free fall condition for a raindrop ends when:
A Weight = buoyant force
B Weight = viscous drag + buoyant force
C Drag becomes zero
D Density changes
Terminal velocity when net force = 0.
Specific heat of a substance is:
A Heat per unit area
B Heat per unit temperature
C Heat required per unit mass per °C
D Heat absorbed per unit time
Standard definition of specific heat.
Coefficient of linear expansion depends on:
A Length
B Mass
C Material
D Temperature only
It is a material constant.
On heating a metal ring, the hole in the middle:
A Decreases
B Increases
C Remains same
D Disappears
Ring expands outward equally → hole enlarges.
Poor conductors of heat are:
A Metals
B Liquids
C Wood, air
D All solids
Non-metals with few free electrons.
Thermal expansion of solids is least for:
A Gases
B Liquids
C Metals
D Solids
Solids expand less since atoms are strongly bound.
Blackbody absorbs:
A Only UV
B Only visible
C Only IR
D All radiation
A blackbody absorbs all incident radiation.
Frost forms on a surface due to:
A Evaporation
B Condensation
C Freezing of vapor (deposition)
D Melting
Vapor → solid transition.
Heat flow direction depends on:
A Conductivity
B Density
C Temperature difference
D Pressure
Heat flows from higher to lower temperature.
Thermal radiation travels with:
A Sound speed
B Speed depending on density
C Speed of light
D Zero velocity
Radiation is electromagnetic → travels at c.
Latent heat of fusion is heat required to:
A Vaporize liquid
B Melt solid
C Heat gas
D Freeze liquid
Fusion = melting.
RMS velocity of gas molecules increases with:
A Pressure
B Temperature
C Density
D Mass
v_rms ∝ √T.
For ideal gas, PV graph at constant temperature is:
A Parabola
B Hyperbola
C Straight line
D Circle
Boyle’s law → PV = constant (rectangular hyperbola).
Internal energy of ideal gas is zero at:
A 0°C
B 273K
C 0 Kelvin
D 100K
U ∝ T, so U = 0 at absolute zero (ideal model).
In isobaric process, heat supplied is partially used for:
A Increasing internal energy only
B Doing external work
C Changing density
D Raising pressure
At constant pressure, system expands → PdV work.
Work done in an isothermal expansion:
A Zero
B Maximum
C Minimum
D Infinite
For given change, isothermal work exceeds adiabatic.
Carnot engine works between T₁ and T₂. Its efficiency:
A Depends on gas type
B Depends on T₂ only
C 1 − T₂/T₁
D T₁/T₂
Carnot efficiency = 1 − (T₂/T₁).
Second law states:
A Heat can fully convert to work
B Work can fully convert to heat
C Heat flows spontaneously from hot to cold
D Temperature depends on work
Fundamental direction of heat flow.
Reversible processes have:
A Maximum entropy production
B Minimum entropy production
C Zero entropy production
D Maximum energy loss
Reversible → ideal → no entropy generation.
A heat engine rejects heat because:
A Waste heat cannot be avoided
B Second law forbids 100% efficiency
C Pressure is low
D Work is too high
No engine can convert all heat into work.
Refrigerator works on:
A Removing work
B Second law of thermodynamics
C Boyle’s law
D Pascal’s law
Heat is extracted from low temperature reservoir using external work → consistent with 2nd law.