If thermal conductivity of a material of wall varies as $$k_0(1 - \alpha T)$$, the temperature at the center of the wall will be ($$\alpha$$ is +ve)
ISRO Scientist or Engineer Mechanical 2010
For the following questions answer them individually
The spectral emissive power $$E_1$$ ; for a diffusely emitting surface is $$E_1 = 0 for \lambda < 3\mu m; E_1 = 150 W/m^2 \mu m for 3 < \lambda < 12 \mu m; E_1 = 300W/m^2 \mu m for 12 < \lambda < 25 \mu m; E_1 = 0 for \lambda > 25 \mu m.$$ The total emissive power of the surface over the entire spectrum is
A wire is plastically deformed bent by supplying a force of 40 N over a distance of 0.8 m. (The force moves in the direction in which the distance is measured). If the wire has a mass of 0.2 kg and a specific heat of $$0.5 kJ/kg.^\circ C$$ estimate the maximum increase in the average temperature of the wire
Two rods one of length L and the other of length 2L are made of the same material and have the same diameter. The two ends of the longer diameter. The two ends of the longer rod are maintained at $$100^\circ C$$. One end of the shorter rod is maintained at $$100^\circ C$$ while the other end is insulated. Both the rods are exposed to the same environment at $$40^\circ C$$. The temperature at the insulated end of the shorter rod is measured to be $$55^\circ C$$. The temperature at the midpoint of the longer rod would be
A sphere, a cube and disc all of the same material, quality and volume are heated to 900 K and left in air. Which of these will have the lowest rate of cooling
Air with initial condition of p1,vl expands to final condition of $$p1/2, 3v_1.$$ The process is
Sun’s surface at 5800 K emits radiation at a wavelength of $$0.5\mu A$$ furnace at $$300^\circ C$$ will emit through a small opening, radiation at a wavelength of
Polytropic index x is given by
The heat flow rate through parallel walls of thickness $$L_1, L_2, and L_3$$ and having surface areas $$A_1, A_2, and A_3$$, thermal conductivities $$k_1, k_2, and k_3,$$ respectively and first and last walls maintained at temperatures $$t_1 and t_2$$ will be
Which of the following property of air does not increase with rise in temperature?
Choose the correct figure representing gas to gas heat transfer in parallel flow heat exchanger?
The value of Prandtl number for air is about
4 body cools from $$90^\circ C to 80^\circ C$$ in 5 minutes. Under the same external conditions to cool from $$80^\circ C to 70^\circ C$$ the body will take
When the temperature of a solid surface changes from $$227^\circ C to 1227^\circ C$$ its total emissive power changes from $$E_1 to E_2.$$ The ratio $$\left(\frac {E_2} {E_1}\right)$$ will be
Characteristic gas constant of a gas is equal to
The matrix $$A = \begin{bmatrix}-4 & -3 & -3 \\1 & 0 & 1 \\4 & 4 & x \end{bmatrix}$$ is its own adjoint. The value of x will be
The temperature of sun can be measured using a
A car moving with uniform acceleration covers 450 m in a 5 second interval, and covers 700 m in the next 5 second interval. The acceleration of the car is
A particle starts from rest with a constant acceleration $$\alpha m/sec^2$$ and after some time it decelerates at a uniform rate of $$\beta 8 m/sec^2$$ till it comes to rest. If the total time taken between two rests positions is t, the maximum velocity acquired by the particle would be
Two metallic blocks having masses in the ratio 2: 3 are made to slide down a friction less inclined plane starting initially from rest position. When these blocks reach the bottom of the inclined plane, they will have their kinetic energies in the ratio
A particle is projected at an angle $$\theta$$ to the horizontal and it attains a maximum height H. The time taken by the projectile to reach the highest point, of its path is
The tension in the cable supporting a lift moving upwards is twice the tension when the lift moves downwards. Whatis the acceleration of the lift?
For the apparent weight of a body at equator to become zero, the earth should rotate with an angular velocity of
A cantilever beam AB of length L and uniform flexural rigidity EI has a bracket AC attached to its free end shown in Fig. Vertical load is applied to the free end C of the bracket. In order that the deflection of point A to be zero the ratio a/L should be
Given that
$$P_E$$ = the crippling load given by Euler
$$P_C$$ = the loadat failure due to direct compression
$$P_R$$ = the load in accordance with the Rankine’s criterion of failure
Then $$P_R$$ is given by
Bending moment M and torque is applied on a solid circular shaft. If the maximum bending stress equals to maximum shear stress developed, them M is equal to
For solid shaft subjected to a torque of 18000 Nm having a permissible shear stress of $$60N/mm^2$$, the diameter of shaft is
Shear force is
Maximum deflection in cantilever due to pure bending moment M atits end is
Maximum shear stress in Mohr’s circle is equal to
Hardness of steel depends on
The modulus of $$1 + \cos \alpha + i \sin \alpha$$ is
Hardnes of martensite is about
Materials after cold working are subjected to following process to relieve stresses
In drop forging the forging is done by
Which of the machine tools can be used for boring
1. Lathe
2. Drilling machine
3. Vertical milling machine
4. Horizontal milling machine
The vernier reading should not be taken at its face value before an actual check has been taken for
High carbon steel carries carbon percentage of
In order to measure/detect materials by non-destructive testing the method generally used is
Shock resisting steels should have
A screw having coefficient of friction equal to or greater than the tangent of the load angle is known as
A bolt is designed with a large factor of safety, on the basis of
For two springs having same stiffness (k) are in series, the equivalent stiffness would be
A material is classified as brittle, if the elongation in a gauge length of 59 mm,is less than
In an extra humid atmosphere which one of the following motor would you select?
In fillet weld throat is
Sensitiveness of a governor is
The value of c which makes the angle $$45^\circ$$ between $$\overline{a} = i + cj$$ and $$\overline{b} = i + j$$ is
For traction applications, the type of motor best suited is
In simple harmonic motion the acceleration is proportional to
A vibro meter
At node of the shaft
Match list I with list II and select the correct answer using the codes. given below the lists.
The cutting speed of the tool in a mechanical shaper is
Which is not correct statement about the function of flux in brazing
Investment casting is used for
Internal and external threads can be produced on tapered surfaces conveniently by
Optical square is
A master gauge is
Dimension of the hole is $$50_{-0.00}^{+0.02} mm $$ and shaft is $$50_{+0.00}^{+0.02} mm. $$ The minimum clearance is
Two cutters are mounted on the arbor so that two faces are machined simultaneously in
The main alloying elements in high speed steel in order of increasing proportion are
Surface roughness on a drawing is represented by
A husband and wife appearin an interview for two vacancies for same post. The probability of husband getting selected is $$\frac {1}{5}$$ while the probability of wife getting selected is $$\frac {1}{7}$$. Then the probability that anyone of them getting selected is
Cylindrical parts are held on planer by
Expressing a dimension as $$25.3^{\pm 0.05} mm is the case of
In comparison to an open-loop system a closed loop system is
The Moody diagram is shown in Fig. The friction factor for turbulent flow in a smooth pipe is given by curve
A piping system consists of three pipes arranged in series, the lengths of the pipes are 1200m, 750 m and 600 m and diameters 750 mm, 600 mm, 450 mm respectively. Transform the system to an equivalent 450 mm diameter pipe
Friction drag is generally larger than the pressure drag in
If D is the diameter of impeller at inlet, w is the width of impeller at inlet and $$V_f$$ is the velocity of flow at inlet, then discharge through a centrifugal pump is equalto
Cavitation parameter is defined by
The maximum thickness of boundary layerin a pipe of radius R is
At a point A in a pipe lilne carrying water, the diameter is 1 m, the pressure 98 KPa and the velocity 1 m/s. At a point B, 2 m higher than A, the diameter is 0.5m and the pressure 20 KPa. The direction of flow would be
In the given figure pressure p in kPa, is
A small plastic boat loaded with pieces of steel rods is floating in a bathtub. If the cargo is dumped into the water allowing the boat to float empty, the water level in the tub will
Four cars, with a mass of 1500 kg each, are loaded on a 6 m wide, 12 m long small car ferry. How far, in cm will it sink in the water?
Water enters a turbine at 900kPa with negligible velocity. What maximum speed, in m/s, can it reach before it enters the turbine rotor?
Given that:
Specific gravity of mercury = 13.6;
Intensity of pressure = 40kPa
Express the intensity of pressure (gauge) in various units (S.I)
The differential equation satisfying $$y = Ae^{3x} + Be^{2x}$$ is
