An expansion process as per law PV = constant is known as
ISRO Scientist or Engineer Mechanical 2018
For the following questions answer them individually
Speed of an aeroplane is measured by
Euler's dimensionless number relates the following
A simple compressible substance inside a cylinder undergoes a change of state quasistatically, isothermally and at constant pressure of 1.5 MPa. If the enthalpy change for the system is 4000 kJ at $$150^\circ C$$, what is the corresponding change in its entropy?
The velocity of sound in a gaseous medium at a temperature of 400 K is 400 m/s. If the temperature of the medium is increased to 600 K, the velocity of sound will be nearly,
Stress strain relation of the Newtonian fluid is
Speed of sound in water is equal to (K-bulk modulus, $$\rho$$-density)
If the stream function of a two dimensional flow is $$\psi = 5 xy$$. then the velocity at a point (3, 4)is
A glass tube of 8 mm diameter is immersed in water. Surface tension of water is 0.0075 kg/m and rise of water in the tube due to capillary effect is
An impulse turbine produces 125 hp under a head of 25 meter. By what percentage should the speed be increased for a head of 100 meter.
The specific speed of a centrifugal pump, delivering 1000litres of water per second against a head of 16 meter at 800 rom
A pipe of 0.1 m$$^2$$ suddenly changes to 0.5 m$$^2$$ area. The quantity of water flowing in the pipe is 0.5 m$$^3$$/s. Head loss due to sudden enlargement is nearly
Efficiency of a centrifugal pump is maximum when the blades are
The critical radius of insulation for a spherical shell is
If the temperature of a solid surface changes from $$27^circ C$$ to $$81^circ C$$, then its emissive power changes in the ratio of nearly
The heat removal rate from a refrigerated space is 7.2 kW and the power input to the compressor is 1.8 kW. The coefficient of performance (COP) of the refrigerator is
For a fluid having Prandtl number equal to unity, the relation between hydrodynamic boundary layer thickness ($$\delta_1$$) and thermal boundary layer thickness ($$\delta_2$$)
Life of a ball bearing at a load of 10 kN is 24000 hours. If the load is increased to 20 kN (all other conditions are same), its life in hour is
The impact strength of a material is an index of its
Which of the following order of crystal structure will match with metals lron-Nickel Titanium in that order at room temperature?
In a machining operation cutting speed is reduced by 50%. Assuming n = 0.5, C = 300 in Taylor's equation. The increase in tool life is
In a linear arc welding process, the heat input per unit length is inversely proportional to
The welding process which uses a blanket of fusible granular flux is
Two non-zero vectors are parallel if their vector productis
If eigen value of a matrix A is $$\lambda$$, then the eigen value of A2 is
The value of $$\lim_{x \rightarrow \infty}\frac{\sin x}{x}$$ is equal to
If $$f(x) = \frac{1 - x}{1 + x}$$ then $$f \left(\frac{1}{x}\right)$$ is equal to
Inverse Laplace transform of $$\frac{S}{S^2 + a^2}$$ is
One dimensional wave equation is
A composite bar made of Aluminium and Steel is fixed rigidly at supports P and Q as shown in figure. When the temperature of the bar is increased by $$10^\circ C$$, the reactions at the supports are (given $$E_{al} = 70 GPa, E_s = 210 GPa, \alpha_{al} = 11E - 6$$ mm/mm$$^\circ C$$ and $$\alpha_s = 12E - 6 mm/mm^\circ C$$)
Torque, Tis applied at the free end of a stepped rod of circular cross-section as shown in figure. If the shear modulus of the material is G, the angular twist, $$\theta$$ at free end will be
In mostbrittle materials, the ultimate strength in compression is larger than the ultimate strength in tension due to
If the natural frequency of a spring mass system on earth is f, its natural frequency on moon where acceleration due to gravity is one-sixth of that on earth will be
A solid shaft can resist a bending moment of 6 KN-m and a torque of 8 kN-m applied together. The maximum torque that the shaft can resist when applied alone is
Two shafts of the same length and material are connectedin series, if the ratio of their diameters is 2, then the ratio of their angles of twist will be
A concentrated load of F acts on a simply supported beam of span L at a distance of $$\frac{L}{3}$$ from left support, the bending momentat this location C is
Euler's critical buckling load for a column fixed at both ends is
A truck hauls a trailer at 60 km/hour when exerting a steady pull of 600 N. If the work is done for 40 minutes, the power required is
A perfectly balanced rotor shaft supported between short bearings at both ends shows a deflection of 2mm at middle. Then the critical speed of the shaft in rom will be nearly,
If an element is loaded as shownin figure below, the von-Mises stress will be close to
The pressure P of a gasin terms of its mean kinetic energy per unit volume E is equal to
Work done in a free expansion process is
If the value of rn is infinitely large in a polytropic process $$PV^n = C$$, then the process is Known as constant
During the charging of a storage battery, the current | is 20 A and the voltage E is 12.8 V. The rate of heat transfer from the battery is 16 W. At whatrate is the internal
energy increasing?
The compression ratio for diesel engines is close to
One kg of carbon monoxide requires, how much quantity of oxygen to produce 11/7 kg of carbondioxide gas
The entropy of water at O K is assumed to be
For an irrotational flow, $$\frac{\partial^2 \phi}{\partial x^2} + \frac{\partial^2 \phi}{\partial y^2} = 0$$ is the equation given by
In a centrifugal pump casing, the flow of water leaving the impeller is
For a two stage reciprocating compressor, compression from P1 to P3 is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the
same polytropic process and the atmospheric pressure is Pa, then the intermediate pressure P2 is given by
The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the
The frequency of ultrasonic waves is
Loudness of the sound does not change with the change in
The hydraulic diameter, $$D_h$$, of a rectangular channel with sides ‘a’ and ‘b’ is
Which of the following has maximum value of thermal conductivity?
The value of Biot number is very small (< 0.01) when
A steam pipe is to be insulated by 2 insulating materials put over each other. For best results
The main objective of ‘shot peening’ is to improve which property of metal parts
A hole is of dimension $$\phi 60^{\frac{+0.015}{-0.000}}$$ and the corresponding shaft is of dimension $$\phi 60^{\frac{+0.011}{-0.001}}$$. When they are assembled they will form a
Which of the following carbon steels is most weldable?
A small percentage of Boron is added to steel in order to
A material that exhibits the same elastic properties in all directions at a point is called
No of atoms per unit cell of a face centered cubic (FCC) lattice is
In asheet metal of 3 mm thickness of a hole of 7 mm diameter needs to be punched. The yield strength in tension of the sheet material is 120 MPa and its ultimate shear strength is 100 MPa. The force required to punch the hole is
Profile of a gear tooth can be checked by
The reflector combined with auto collimator can be used for checking
PERT has following time estimate
Which of the following is an amorphous material?
In a party, each person shook hands with every other person present. The total number of hand shakes was 45. The number of people in the part are
Which of the following method is said to be a direct method in numerical methods?
‘If X is a normal variable with mean $$\mu$$ and standard deviation $$\sigma$$, then the mean and standard deviation of the variable $$Z = \frac{X - \mu}{\sigma}$$ is
Example for an elliptic partial differential equation is
The solution of the equation $$y'' + y = 0$$ satisfy the condition $$y(0) = 1, y\left(\frac{\pi}{2}\right) = 2$$, is
For the spring system given in figure, the equivalent stiffness is
A round uniformly tapered bar of length L and Young’s modulus E has diameter of ‘a’ at one end and ‘2d’ at the other end. If the bar is pulled by an axial force F, the extension produced will be
Two blocks A and B of 1 kg each are kept on flat surface, one above other. The coefficient of friction between each contacting pair is 0.2. If the lower block is pulled with a horizontal force F, the minimum value of F for which the slip occurs between the blocks is nearly
A solid metal bar of uniform diameter D and length L is hung vertically. If $$\rho$$ is density and E is the Young’s modulus, then the total elongation due to self weight is
A circular solid disc of uniform thickness 20 mm, radius 400 mm and mass 10 kg, is used as a flywheel. If it rotates at 300 rom, the kinetic energy of the flywheel, in Joules is
If the length of the cantilever beam is reduced to $$\frac{1}{4}th$$, the natural frequency of the mass M at the end of this cantilever beam of negligible mass will be increased by a factor of
The relationship between the linear elastic properties Young’s modulus (E), rigidity modulus (G) and Bulk modulus (K) is given by
