⚙️ Mechanical Eng Solved MCQs with Answers

Practice 934 approved ⚙️ Mechanical Eng questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

934 solved MCQs

Wien's displacement law is ______?Answer: 𝜆𝑚𝑇= constant The hydrogen-like atom has one electron revolving around a stationary nucleus. The energy required to execute electron from the second orbit to the third orbit is 42.7eV. The atomic number of the atom is _______?Answer: 3 2D1/2 will split into ______ components in magnetic field.Answer: 4 A particle executing simple harmonic motion of amplitude 5 cm has maximum speed of 31.4 cm/s. The frequency of its oscillation is ______?Answer: 1 Hz Solar radiation emitted by sun resembles that emitted by a black body at a temperature of 6000K. Maximum intensity is emitted at a wavelength of about 4800A°. If the sun was cooled down from 6000 K to 3000 K then the peak intensity would occur at a wavelength of ______?Answer: 9600A˚ A wooden box is sitting on a table. The normal force on the box from the table is 75 N. A second identical box is placed on top of the first box. The normal forces on the first box by the table will ______?Answer: Increase to 150 N The coefficient of transmission and coefficient of reflection for a given body at a given temperature are 0.33 and 0.64 respectively. Then the coefficient of emission of the same body at the same temperature will be ______?Answer: 0.03 Bosons have symmetrical wave functions. They do not obey ______?Answer: Pauli’s Exclusion Principle An atom can radiate at any time after it is excited. It is found that in a typical case, the average excited atom has a lifetime of about 10^(-8) s. That is, during this period it emits a photon and is de-excited. What is the minimum uncertainty delta-v in the frequency of the photon?Answer: 8 x 10^6 Hz Packing density is maximum for _______?Answer: Face centered cubic lattice The energy value up to which all energy states are full at At absolute zero (0K) and above which all states are empty is known as _____?Answer: Fermi energy The moment of inertia of a thin uniform disk about an axis passing through its centre and perpendicular to its plane is MR^2/2, then its M.I about a tangent parallel to its diameter is ______?Answer: 5/4 MR^2 The fundamental frequency of string stretched with a weight of 4kg is 256 Hz. The weight required to produce its octave is _____?Answer: 16 kg wt To obtain a p-type semiconductor germanium crystal, it must be doped with foreign atoms whose valency is _____?Answer: 3 Which of the following is a false statement about atomic solids?Answer: All atomic solids have high melting points What equation does the velocity potential of an incompressible fluid satisfy?Answer: Laplace's equation What is the boundary condition at a fixed boundary of the inviscid fluid?Answer: u . n = 0, where n is the null normal to the boundary If Hessian Matric H is zero at any point, then the point is called?Answer: Parabolic A Carnot engine, with its cold body at 17°C, has 50% efficiency. If the temperature of its hot body is now increased by 145°C, the efficiency becomes _____?Answer: 60% At resonance, which of the following is maximum?Answer: Amplitude The process in which pressure remains constant is called ______?Answer: Isobaric The change in Entropy is zero for _____?Answer: Reversible adiabatic processes Pressure of a gas is directly proportional to _______?Answer: Kinetic energy What is the degree of freedom in the case of a monoatomic gas?Answer: 3 If momentum decreases by 20% kinetic energy will decrease _____?Answer: 36% If momentum decreases by 20% kinetic energy will decrease _____?Answer: 36% A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of 3000°K, which of these will cool fastest?Answer: Plate The atomic diameter of a BCC crystal (if a is lattice parameter) is _____?Answer: a/(4/√3) A physical system undergoing forced vibration is called?Answer: Frequency harmonic oscillation What happens when the stress applied to the body is increased beyond the maximum value and is removed after some time?Answer: The body cannot return to its original position