List of top Mechanical Engineering Questions

The undamped natural frequency of system is 80 rad/sec. A damper is provided in the system having damping factor 0.7. The damped natural frequency of the system in rad/sec will be:
For the same compression ratio and same heat supplied in Otto, Diesel and Dual cycles:
(A) Otto cycle has maximum efficiency.
(B) Diesel cycle has minimum heat rejected.
(C) Dual cycle has maximum heat rejected.
(D) Diesel cycle has maximum heat rejected.
Choose the correct answer from the options given below.
In a simple saturated Vapour compression refrigeration cycle, the enthalpy at various state points are: 10 kJ/kg, 45 kJ/kg and 25 kJ/kg. The mass flow rate of refrigerant is 2 kg/s:
  1. The power consumption of compressor is 40 kJ/kg
  2. The refrigeration capacity is 70 kW
  3. The COP is 1.75
  4. Heat rejected in condenser is 110 kW
Choose the correct answer from the options given below.
Assertion (A): In heating and dehumidification of air, relative humidity of air decreases.
Reason (R): Sensible heating causes enthalpy to decrease.
In light of the above statements, choose the correct answer from the options given below.
The instantaneous centre of a sliding body moving on a stationary curved surface lies at
With increase in pressure ratio in Brayton cycle the net work output
A thermo flask is
2 kg of air is contained in a closed system at a pressure of 2 bar and 0.5 m3. It undergoes an isobaric expansion till the final volume becomes 0.6 m3. The work transfer (in kJ) during the process is:
Given below are two statements:
Statement (I): The heat transfer coefficient for air in free convection varies between 5 to 30 W/m2·K.
Statement (II): The heat transfer coefficient of steam during condensation lies between 5000 to 110000 W/m2·K.
In light of the above statements, choose the most appropriate answer from the options given below.
Given below are two statements, one is labelled as Assertion (A) and the other one labelled as Reason (R):
Assertion (A): The Clausius statement of second law of thermodynamics states that it is impossible to transfer heat from a body at low temperature to a body at high temperature without the aid of external work.
Reason (R): Heat always flows from low temperature to high temperature.
In light of the above statements, choose the correct answer from the options given below:
A system at 500 K receives 7200 kJ/min of heat from a source at 1000 K The ambient temperature is 300 K The system and source temperature remain constant during heat transfer The decrease in available energy due to heat transfer through finite temperature difference is
The shape factor of a hemispherical body placed on a flat surface with respect to itself is
Lumped Heat capacity analysis can be applied to a system when
Given below are two statements:
Statement (A): The flow in a pipe is turbulent when the Reynolds’ Number is more than 4000.
Statement (R): The flow in a pipe is turbulent at entry and slowly changes to laminar along the length of the pipe.
In light of the above statements, choose the correct answer from the options given below:
Consider the following statements about the flow in a convergent-divergent nozzle operating under design conditions:
  1. In the divergent section, pressure is higher than the pressure in the convergent section.
  2. The pressure at the throat is equal to critical pressure.
  3. The pressure in the convergent section reduces.
  4. The flow is subsonic in the convergent section and supersonic in the divergent section.
Choose the correct answer from the options given below.
Given below are two statements one is labelled as Assertion A and the other one labelled as Reason R
The vacuum in a closed container is 50 mm of Hg The absolute pressure in the container is
Consider the following statements: The assumptions made in deriving Euler’s equation are:
  1. Fluid is non-viscous fluid.
  2. The flow is along a streak line.

The figure shows a block of mass \(m = 20\) kg attached to a pair of identical linear springs, each having a spring constant \(k = 1000\) N/m. The block oscillates on a frictionless horizontal surface. Assuming free vibrations, the time taken by the block to complete ten oscillations is ............... seconds. (Rounded off to two decimal places) Take \(\pi = 3.14\). 

Consider a unidirectional fluid flow with the velocity field given by
\(V(x, y, z, t) = u(x, t)\ \hat{i}\)
where \(u(0, t) = 1\). If the spatially homogeneous density field varies with time \(t\) as
\(\rho(t) = 1 + 0.2e^{-t}\), the value of \(u(2,1)\) is ................ (Rounded off to two decimal places).
Assume all quantities to be dimensionless.

An explosion at time \(t = 0\) releases energy \(E\) at the origin in a space filled with a gas of density \(\rho\). Subsequently, a hemispherical blast wave propagates radially outwards as shown in the figure. 
Let \(R\) denote the radius of the front of the hemispherical blast wave. The radius \(R\) follows the relationship \(R = k t^a E^b \rho^c\), where \(k\) is a dimensionless constant. The value of exponent \(a\) is ................ 
(Rounded off to one decimal place) 

 

The figure shows two fluids held by a hinged gate. The atmospheric pressure is \(P_a\) = 100 kPa. The moment per unit width about the base of the hinge is ............... kNm/m. (Rounded off to one decimal place) 
Take the acceleration due to gravity to be g = 9.8 m/s². 

 

An optical flat is used to measure the height difference between a reference slip gauge A and a slip gauge B. Upon viewing via the optical flat using a monochromatic light of wavelength 0.5 \(\mu\)m, 12 fringes were observed over a length of 15 mm of gauge B. If the gauges are placed 45 mm apart, the height difference of the gauges is ............... \(\mu\)m. (Answer in integer) 

A solid part (see figure) of polymer material is to be fabricated by additive manufacturing (AM) in square-shaped layers starting from the bottom of the part working upwards. The nozzle diameter of the AM machine is a/10 mm and the nozzle follows a linear serpentine path parallel to the sides of the square layers with a feed rate of a/5 mm/min. Ignore any tool path motions other than those involved in adding material, and any other delays between layers or the serpentine scan lines. The time taken to fabricate this part is ............... minutes. (Answer in integer) 

 

A coordinate measuring machine (CMM) is used to determine the distance between Surface SP and Surface SQ of an approximately cuboidal shaped part. Surface SP is declared as the datum as per the engineering drawing used for manufacturing this part. The CMM is used to measure four points P1, P2, P3, P4 on Surface SP, and four points Q1, Q2, Q3, Q4 on Surface SQ as shown. A regression procedure is used to fit the necessary planes. The distance between the two fitted planes is ............... mm. (Answer in integer)