Hot questions in Fluid Mechanics and Thermal Sciences / GO Mechanical

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GATE2016-2-44
A piston-cylinder device initially contains $0.4 \: m^3$ of air (to be treated as an ideal gas) at $100 \: kPa$ and $80^ \circ C$. The air is now isothermally compressed to $0.1 \: m^3$. The work done during this process is ________ $kJ$.

A piston-cylinder device initially contains $0.4 \: m^3$ of air (to be treated as an ideal gas) at $100 \: kPa$ and $80^ \circ C$. The air is now isothermally compressed ...

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GATE2015-2-54
A project consists of $7$ activities. The network along with the time durations (in days) for various activities is shown in the figure. The minimum time (in days) for completion of the project is_________

A project consists of $7$ activities. The network along with the time durations (in days) for various activities is shown in the figure.The minimum time (in days) for com...

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GATE2015-2-46
For the same values of peak pressure, peak temperature and heat rejection, the correct order of efficiencies for Otto, Dual and Diesel cycles is $\eta _{\text{Otto}}> \eta _{\text{Dual}}> \eta _{\text{Diesel}}$ ... $\eta _{\text{Diesel}}> \eta _{\text{Otto}}> \eta _{\text{Dual}}$

For the same values of peak pressure, peak temperature and heat rejection, the correct order of efficiencies for Otto, Dual and Diesel cycles is$\eta _{\text{Otto}} \eta ...

Arjun

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GATE2016-2-15
A hollow cylinder has length $L$, inner radius $r_1$, outer radius $r_2$, and thermal conductivity $k$. The thermal resistance of the cylinder for radial conduction is $\dfrac{\ln(r_2/r_1)}{2\pi kL} \\$ $\dfrac{\ln(r_1/r_2)}{2\pi kL} \\$ $\dfrac{2\pi kL}{\ln(r_2/r_1)} \\$ $\dfrac{2\pi kL}{\ln(r_1/r_2)}$

A hollow cylinder has length $L$, inner radius $r_1$, outer radius $r_2$, and thermal conductivity $k$. The thermal resistance of the cylinder for radial conduction is$\d...

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GATE2015-2-41
For a fully developed laminar flow of water (dynamic viscosity $0.001$ $P_{a-s}$) through a pipe of radius $5$ $cm$, the axial pressure gradient is −$10$ $Pa/m$. The magnitude of axial velocity (in $m/s$) at a radial location of $0.2$ $cm$ is _______

For a fully developed laminar flow of water (dynamic viscosity $0.001$ $P_{a-s}$) through a pipe of radius $5$ $cm$, the axial pressure gradient is −$10$ $Pa/m$. The ma...

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GATE2015-1-54
A well insulated rigid container of volume $1 \: m^3$ contains $1.0 \: kg$ of an ideal gas $[C_p = 1000 \: J/(kg\cdot K)$ and $C_v=800 J/(kg \cdot K)]$ at a pressure of $105 \: Pa$. A stirrer is rotated at constant rpm in the container for $1000$ rotations and the applied torque is $100 \: N-m$. The final temperature of the gas (in $K$) is $500.0$ $773.0$ $785.4$ $1285.4$

A well insulated rigid container of volume $1 \: m^3$ contains $1.0 \: kg$ of an ideal gas $[C_p = 1000 \: J/(kg\cdot K)$ and $C_v=800 J/(kg \cdot K)]$ at a pressure of ...

Arjun

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GATE2016-2-18
The heat removal rate from a refrigerated space and the power input to the compressor are $7.2$ $kW$ and $1.8$ $kW$, respectively. The coefficient of performance (COP) of the refrigerator is ______

The heat removal rate from a refrigerated space and the power input to the compressor are $7.2$ $kW$ and $1.8$ $kW$, respectively. The coefficient of performance (COP) of...

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GATE2016-1-40
Oil (kinematic viscosity, $v_{\text{oil}}=1.0\times 10^{-5} \:m^2/s$) flows through a pipe of $0.5$ $m$ diameter with a velocity of $10$ $m/s$. Water (kinematic viscosity, $v_w=0.89\times 10^{-6}\:m^2/s$) is flowing through a model pipe of diameter $20 \:mm$. For satisfying the dynamic similarity, the velocity of water (in $m/s$) is __________

Oil (kinematic viscosity, $v_{\text{oil}}=1.0\times 10^{-5} \:m^2/s$) flows through a pipe of $0.5$ $m$ diameter with a velocity of $10$ $m/s$. Water (kinematic viscosity...

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GATE2016-1-42
A steel ball of $10\:mm$ diameter at $1000\:K$ is required to be cooled to $350\:K$ by immersing it in a water environment at $300\:K$. The convective heat transfer coefficient is $1000\:W/m^2-K$. Thermal conductivity of steel is $40\:W/m-K$. The time constant for the cooling process $\tau$ is $16\:s$. The time required (in $s$) to reach the final temperature is __________

A steel ball of $10\:mm$ diameter at $1000\:K$ is required to be cooled to $350\:K$ by immersing it in a water environment at $300\:K$. The convective heat transfer coeff...

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GATE2015-1-53
Water $(\rho = 1000 \: kg/m^3)$ flows through a venturimeter with inlet diameter $80 \: mm$ and throat diameter $40 \: mm$. The inlet and throat gauge pressures are measured to be $400 \: kPa$ and $130 \: kPa$ respectively. Assuming the venturimeter to be horizontal and neglecting friction, the inlet velocity (in $m/s$) is _______

Water $(\rho = 1000 \: kg/m^3)$ flows through a venturimeter with inlet diameter $80 \: mm$ and throat diameter $40 \: mm$. The inlet and throat gauge pressures are measu...

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GATE2016-3-16
Grashof number signifies the ratio of inertia force to viscous force buoyancy force to viscous force buoyancy force to inertia force inertia force to surface tension force

Grashof number signifies the ratio ofinertia force to viscous forcebuoyancy force to viscous forcebuoyancy force to inertia forceinertia force to surface tension force

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GATE2016-1-18
Consider two hydraulic turbines having identical specific speed and effective head at the inlet. If the speed ratio $\displaystyle{\left(\frac{N_1}{N_2}\right)}$ of the two turbines is $2$, then the respective power ratio $\displaystyle{\left(\frac{P_1}{P_2}\right)}$ is _____________

Consider two hydraulic turbines having identical specific speed and effective head at the inlet. If the speed ratio $\displaystyle{\left(\frac{N_1}{N_2}\right)}$ of the t...

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GATE2016-1-47
In a steam power plant operating on an ideal Rankine cycle, superheated steam enters the turbine at $3 \: MPa$ and $350^ \circ C$. The condenser pressure is $75$ $kPa$. The thermal efficiency of the cycle is ________ percent. Given data: For saturated liquid, at $P=75 \:kPa$ ... $T=350^\circ C$ (superheated steam), $h=3115.3 \: kJ/kg$, $s=6.7428 \: kJ/kg-K$

In a steam power plant operating on an ideal Rankine cycle, superheated steam enters the turbine at$3 \: MPa$ and $350^ \circ C$. The condenser pressure is $75$ $kPa$. Th...

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GATE2016-2-42
Consider a parallel-flow heat exchanger with area $A_p$ and a counter-flow heat exchanger with area $A_c$ . In both the heat exchangers, the hot stream flowing at $1 \: kg/s$ cools from $80^\circ C$ to $50^\circ C$. For the cold stream ... exchangers are of the same fluid. Also, both the heat exchangers have the same overall heat transfer coefficient. The ratio $A_c/A_p$ is _________

Consider a parallel-flow heat exchanger with area $A_p$ and a counter-flow heat exchanger with area $A_c$ . In both the heat exchangers, the hot stream flowing at $1 \: k...

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GATE2015-2-13
Which of the following statements regarding a Rankine cycle with reheating are TRUE? increase in average temperature of heat addition reduction in thermal efficiency drier steam at the turbine exit only $(i)$ and $(ii)$ are correct only $(ii)$ and $(iii)$ are correct only $(i)$ and $(iii)$ are correct $(i)$, $(ii)$ and $(iii)$ are correct

Which of the following statements regarding a Rankine cycle with reheating are TRUE?increase in average temperature of heat additionreduction in thermal efficiencydrier s...

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GATE2016-3-17
The INCORRECT statement about the characteristics of critical point of a pure substance is that there is no constant temperature vaporization process it has point of inflection with zero slope the ice directly converts from solid phase to vapor phase saturated liquid and saturated vapor states are identical

The INCORRECT statement about the characteristics of critical point of a pure substance is thatthere is no constant temperature vaporization processit has point of inflec...

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GATE2016-3-41
For a two-dimensional flow, the velocity field is $\overrightarrow{u}=\dfrac{x}{x^2+y^2}\hat{i}+\dfrac{y}{x^2+y^2}\hat{j}$ where$\hat{i}$ and $\hat{j}$ are the basis vectors in the $x-y$ Cartesian coordinate system. Identify the CORRECT statements from below. The flow is incompressible. The flow is ... $(2)$ and $(3)$ $(1)$ and $(3)$ $(1)$ and $(2)$ $(3)$ and $(4)$

For a two-dimensional flow, the velocity field is $\overrightarrow{u}=\dfrac{x}{x^2+y^2}\hat{i}+\dfrac{y}{x^2+y^2}\hat{j}$ where$\hat{i}$ and $\hat{j}$ are the basis vec...

Arjun

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GATE2015-3-40
A solid sphere $1$ of radius ‘$r$’ is placed inside a hollow, closed hemispherical surface $2$ of radius ‘$4r$’. The shape factor $F_{2-1}$ is $1/12$ $1/2$ $2$ $12$

A solid sphere $1$ of radius ‘$r$’ is placed inside a hollow, closed hemispherical surface $2$ of radius ‘$4r$’. The shape factor $F_{2-1}$ is$1/12$$1/2$$2$$12$

Arjun

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GATE2015-1-47
For flow through a pipe of radius $R$, the velocity and temperature distribution are as follows: $u(r,x)=C_1,$, and $T(r,x)=C_2[1- \left (\dfrac{r}{R} \right )^3]$ where $C_1$ and $C_2$ ... mean velocity of flow. The value of $T_m$ is $\dfrac{0.5C_2}{U_m} \\$ $0.5C_2 \\$ $0.6C_2 \\$ $\dfrac{0.6C_2}{U_m}$

For flow through a pipe of radius $R$, the velocity and temperature distribution are as follows:$u(r,x)=C_1,$, and $T(r,x)=C_2[1- \left (\dfrac{r}{R} \right )^3]$ where $...

Arjun

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GATE2015-3-25
An air-standard Diesel cycle consists of the following processes: $1 - 2$: Air is compressed isentropically. $2 - 3$: Heat is added at constant pressure. $3 - 4$: Air expands isentropically to the original volume. $4 - 1$: Heat is rejected at constant volume. If $\gamma$ ... $1-\displaystyle{\frac{T_4-T_1}{(\gamma -1)(T_3-T_2)}}$

An air-standard Diesel cycle consists of the following processes:$1 – 2$: Air is compressed isentropically.$2 – 3$: Heat is added at constant pressure.$3 – 4$: Air ...

Arjun

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GATE2016-3-44
Steam at an initial enthalpy of $100$ $kJ/kg$ and inlet velocity of $100$ $m/s$, enters an insulated horizontal nozzle. It leaves the nozzle at $200$ $m/s$. The exit enthalpy (in $kJ/kg$) is __________

Steam at an initial enthalpy of $100$ $kJ/kg$ and inlet velocity of $100$ $m/s$, enters an insulated horizontal nozzle. It leaves the nozzle at $200$ $m/s$. The exit enth...

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GATE2016-3-45
In a mixture of dry air and water vapor at a total pressure of $750$ $mm$ of $Hg$, the partial pressure of water vapor is $20$ $mm$ of $Hg$. The humidity ratio of the air in grams of water vapor per $kg$ of dry air ($g_w/kg_{da}$) is __________

In a mixture of dry air and water vapor at a total pressure of $750$ $mm$ of $Hg$, the partial pressure of water vapor is $20$ $mm$ of $Hg$. The humidity ratio of the air...

Arjun

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GATE2015-3-37
Refrigerant vapor enters into the compressor of a standard vapor compression cycle at −$10^\circ C \:(h = 402 \: kJ/kg)$ and leaves the compressor at $50^\circ C \: (h = 432 \: kJ/kg)$. It leaves the condenser at $30^\circ C \: (h = 237 \: kJ/kg)$. The COP of the cycle is ________

Refrigerant vapor enters into the compressor of a standard vapor compression cycle at −$10^\circ C \:(h = 402 \: kJ/kg)$ and leaves the compressor at $50^\circ C \: (h ...

Arjun

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GATE2015-2-15
If a foam insulation is added to a $4 \: cm$ outer diameter pipe as shown in the figure, the critical radius of insulation (in $cm$) is _____________

If a foam insulation is added to a $4 \: cm$ outer diameter pipe as shown in the figure, the critical radius of insulation (in $cm$) is _____________

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GATE2015-2-40
The head loss for a laminar incompressible flow through a horizontal circular pipe is $h_1$. Pipe length and fluid remaining the same, if the average flow velocity doubles and the pipe diameter reduces to half its previous value, the head loss is $h_2$. The ratio $h_2$/$h_1$ is $1$ $4$ $8$ $16$

The head loss for a laminar incompressible flow through a horizontal circular pipe is $h_1$. Pipe length and fluid remaining the same, if the average flow velocity double...

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GATE ME 2013 | Question: 18
In order to have maximum power from a Pelton turbine, the bucket speed must be equal to the jet speed. equal to half of the jet speed. equal to twice the jet speed. independent of the jet speed.

In order to have maximum power from a Pelton turbine, the bucket speed must beequal to the jet speed.equal to half of the jet speed.equal to twice the jet speed.independe...

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piyag476 asked Feb 19, 2017

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GATE2015-1-13
A wheel of radius $r$ rolls without slipping on a horizontal surface shown below. If the velocity of point $P$ is $10$ $m/s$ in the horizontal direction, the magnitude of velocity of point $Q$ (in $m/s$) is ______

A wheel of radius $r$ rolls without slipping on a horizontal surface shown below. If the velocity of point $P$ is $10$ $m/s$ in the horizontal direction, the magnitude of...

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GATE2016-2-45
A reversible cycle receives $40 \: kJ$ of heat from one heat source at a temperature of $127^ \circ C$ and $37 \: kJ$ from another heat source at $97^ \circ C$. The heat rejected (in $kJ$) to the heat sink at $47^ \circ C$ is __________

A reversible cycle receives $40 \: kJ$ of heat from one heat source at a temperature of $127^ \circ C$ and $37 \: kJ$ from another heat source at $97^ \circ C$. The heat ...

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GATE2016-2-46
A refrigerator uses $R-134a$ as its refrigerant and operates on an ideal vapour-compression refrigeration cycle between $0.14 \: MPa$ and $0.8 \: MPa$.if the mass flow rate of refrigerant is $0.05 \: kg/s$,the rate of heat rejection to the environment is_______$kW$ ... $\text{At } P=0.8 \: MPa, \: h=93.42 \: kJ/kg, \: \text{ (saturated liquid) }$

A refrigerator uses $R-134a$ as its refrigerant and operates on an ideal vapour-compression refrigeration cycle between $0.14 \: MPa$ and $0.8 \: MPa$.if the mass flow ra...

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GATE2015-1-11
Air enters a diesel engine with a density of $1.0$ $kg$/$m^3$. The compression ratio is $21$. At steady state, the air intake is $30 × 10^{-3}$ $kg/s$ and the net work output is $15$ $kW$. The mean effective pressure (in $kPa$) is ____________

Air enters a diesel engine with a density of $1.0$ $kg$/$m^3$. The compression ratio is $21$. At steady state, the air intake is $30 × 10^{-3}$ $kg/s$ and the net work o...

Arjun

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GATE2016-3-13
A channel of width $450$ $mm$ branches into two sub-channels having width $300$ $mm$ and $200$ $mm$ as shown in figure. If the volumetric flow rate (taking unit depth) of an incompressible flow through the main channel is $0.9$ $m^3/s$ and the velocity ... velocity in the sub-channel of width $300$ $mm$ is _____________ $m/s$. Assume both inlet and outlet to be at the same elevation.

A channel of width $450$ $mm$ branches into two sub-channels having width $300$ $mm$ and $200$ $mm$ as shown in figure. If the volumetric flow rate (taking unit depth) of...

Arjun

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GATE2016-3-46
In a $3$-stage air compressor, the inlet pressure is $p_1$, discharge pressure is $p_4$.and the intermediate pressures are $p_2$ and $p_3 ( p_2 < p_3)$. The total pressure ratio of the compressor is $10$ and the pressure ratios of the stages are equal. If $p_1 = 100$ $kPa$, the value of the pressure $p_3$ (in $kPa$) is __________

In a $3$-stage air compressor, the inlet pressure is $p_1$, discharge pressure is $p_4$.and the intermediate pressures are $p_2$ and $p_3 ( p_2 < p_3)$. The total pressur...

Arjun

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GATE2015-3-12
Saturated vapor is condensed to saturated liquid in a condenser. The heat capacity ratio is $C_r = \displaystyle{\frac{C_{\text{min}}}{C_{\text{max}}}}$. The effectiveness $(\varepsilon)$ of the condenser is $\displaystyle{\frac{1-\text{exp}[-NTU(1+C_r)]}{1+C_r}} \\$ ... $\displaystyle{\frac{NTU}{1+NTU}} \\$ $1 - \text{exp}(-NTU)$

Saturated vapor is condensed to saturated liquid in a condenser. The heat capacity ratio is $C_r = \displaystyle{\frac{C_{\text{min}}}{C_{\text{max}}}}$. The effectivenes...

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GATE2016-2-16
Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is $R_o$ and that of the inner cylinder is $R_i$ . The radiation view factor of the outer cylinder onto itself is $1-\sqrt{\dfrac{R_i}{R_o}}\\$ $\sqrt{1-\dfrac{R_i}{R_o}} \\$ $1-\dfrac{R_i}{R_o}^{1/3} \\$ $1-\dfrac{R_i}{R_o}$

Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is $R_o$ and that of the inner cylinde...

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GATE2016-1-49
Heat is removed from a molten metal of mass $2$ $kg$ at a constant rate of $10$ $kW$ till it is completely solidified.The cooling curve is shown in the figure Assuming uniform temperature throughout the volume of the metal during solidification,the latent heat of fusion of metal ( in $kJ$/$kg$) is _________

Heat is removed from a molten metal of mass $2$ $kg$ at a constant rate of $10$ $kW$ till it is completely solidified.The cooling curve is shown in the figureAssuming uni...

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GATE2015-1-8
For flow of viscous fluid over a flat plate, if the fluid temperature is the same as the plate temperature, the thermal boundary layer is thinner than the velocity boundary layer thicker than the velocity boundary layer of the same thickness as the velocity boundary layer not formed at all

For flow of viscous fluid over a flat plate, if the fluid temperature is the same as the plate temperature, the thermal boundary layer isthinner than the velocity boundar...

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GATE2015-2-39
The total emissive power of a surface is $500 \: W/ m^2$ at a temperature $T_1$ and $1200 \: W/m^2$ at a temperature $T_2$, where the temperatures are in Kelvin. Assuming the emissivity of the surface to be constant, the ratio of the temperatures $\dfrac{T_1}{T_2}$ is $0.308$ $0.416$ $0.803$ $0.874$

The total emissive power of a surface is $500 \: W/ m^2$ at a temperature $T_1$ and $1200 \: W/m^2$ at a temperature $T_2$, where the temperatures are in Kelvin. Assuming...

Arjun

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GATE2016-3-18
For a heat exchanger, $\triangle T_{\text{max}}$ is the maximum temperature difference and $\triangle T_{\text{min}}$ is the minimum temperature difference between the two fluids. LMTD is the log mean temperature difference. $C_{\text{min}}$ and $C_{\text{max}}$ are the minimum ... $C_{\text{max}} \triangle T_{\text{max}}$ $C_{\text{max}} \triangle T_{\text{min}}$

For a heat exchanger, $\triangle T_{\text{max}}$ is the maximum temperature difference and $\triangle T_{\text{min}}$ is the minimum temperature difference between the tw...

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GATE2016-2-47
The partial pressure of the water vapour in a moist air sample of relative humidity $70\%$ is $1.6 \: kPa$,the total pressure being $101.35 \: kPa$ ... where $p_o=101.325 \: kPa$. The dry bulb temperature of the moist air sample (in $_{}^{\circ}\textrm{C}$) is

The partial pressure of the water vapour in a moist air sample of relative humidity $70\%$ is $1.6 \: kPa$,the total pressure being $101.35 \: kPa$.moist air may be treat...

Arjun

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GATE2016-2-35
A circular metallic rod of length $250 \: mm$ is placed between two rigid immovable walls as shown in the figure. The rod is in perfect contact with the wall on the left side and there is a gap of $0.2 \: mm$ between the rod and the wall on the right side. If the ... material of the rod is $200 \: GPa$ and the coefficient of thermal expansion is $10^{−5}$ per $_{}^{\circ}\textrm{C}$.

A circular metallic rod of length $250 \: mm$ is placed between two rigid immovable walls as shown in the figure. The rod is in perfect contact with the wall on the left ...

Arjun

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