# Engineering Mechanics Interview Questions and Answers

Contents

## Q: What is Engineering Mechanics?

A: Engineering mechanics is the branch of engineering that deals with the behavior of physical bodies when subjected to forces or displacements, and the effects of these actions on the environment around them.

## Q: What is Newton’s First Law of Motion?

A: Newton’s first law of motion states that a body at rest will remain at rest, and a body in motion will continue to move with constant velocity, unless acted upon by a net external force.

## Q: What is Newton’s Second Law of Motion?

A: Newton’s second law of motion states that the acceleration of a body is directly proportional to the net external force acting on it, and inversely proportional to its mass.

## Q: What is Newton’s Third Law of Motion?

A: Newton’s third law of motion states that for every action, there is an equal and opposite reaction.

## Q: What is the difference between a scalar and a vector quantity?

A: A scalar quantity has only magnitude, while a vector quantity has both magnitude and direction.

## Q: What is a free-body diagram?

A: A free-body diagram is a schematic representation of a physical body or system, indicating all the forces acting on it.

## Q: What is the principle of conservation of energy?

A: The principle of conservation of energy states that energy cannot be created or destroyed, but can only be converted from one form to another.

## Q: What is a moment of a force?

A: A moment of a force, also known as torque, is the product of the force and the perpendicular distance between the line of action of the force and a reference point.

## Q: What is the difference between statics and dynamics?

A: Statics deals with the study of physical bodies and systems at rest or in equilibrium, while dynamics deals with the study of physical bodies and systems in motion, and the forces and energy involved in their motion.

## Q: What is the difference between stress and strain?

A: Stress is the internal force per unit area of a material, while strain is the deformation of a material in response to stress.

## Q: What is the difference between elastic and plastic deformation?

A: Elastic deformation is a reversible deformation of a material, in which it returns to its original shape when the stress is removed, while plastic deformation is an irreversible deformation of a material, in which it undergoes permanent deformation even after the stress is removed.

## Q: What is the difference between a beam and a column?

A: A beam is a structural element that is designed to resist bending, while a column is a structural element that is designed to resist compressive forces.

## Q: What is the difference between a truss and a frame?

A: A truss is a structural element that is composed of straight members connected at joints, while a frame is a structural element that is composed of interconnected beams and columns.

## Q: What is the difference between a determinate and indeterminate structure?

A: A determinate structure is a structure in which the internal forces and reactions can be determined solely by using equilibrium equations, while an indeterminate structure is a structure in which the internal forces and reactions cannot be determined by using equilibrium equations alone.

## Q: What is the difference between a statically determinate and statically indeterminate structure?

A: A statically determinate structure is a structure in which the number of unknown internal forces and reactions is equal to the number of available equilibrium equations, while a statically indeterminate structure is a structure in which the number of unknown internal forces and reactions is greater than the number of available equilibrium equations.

## Q: What is the difference between a simple and a compound machine?

A: A simple machine is a device that performs a single, basic mechanical function, such as a lever or a pulley, while a compound machine is a device that combines two or more simple machines to perform a more complex mechanical function, such as a bicycle or a car.

## Q: What is the difference between a kinematic chain and a mechanism?

A: A kinematic chain is a series of connected links or elements that transmit motion or force, while a mechanism is a device that performs a specific function by transforming motion or force.

## Q: What is the difference between kinematics and kinetics?

A: Kinematics deals with the motion of bodies and systems without considering the forces that cause the motion, while kinetics deals with the forces and energy involved in the motion of bodies and systems.

## Q: What is the difference between linear motion and rotational motion?

A: Linear motion is motion in a straight line, while rotational motion is motion around an axis or a point.

## Q: What is the difference between velocity and acceleration?

A: Velocity is the rate of change of position with respect to time, while acceleration is the rate of change of velocity with respect to time.

## Q: What is Hooke’s Law?

A: Hooke’s Law states that the deformation of a material is directly proportional to the applied force, within the elastic limit of the material.

## Q: What is the difference between a bearing and a bushing?

A: A bearing is a mechanical component that supports a rotating shaft or other moving part, while a bushing is a cylindrical lining that provides a bearing surface for a rotating or sliding shaft or other moving part.

## Q: What is the difference between a gear and a pulley?

A: A gear is a mechanical component that transmits power and motion between two or more rotating shafts, while a pulley is a mechanical component that transmits power and motion between a rotating shaft and a belt or a chain.

## Q: What is the difference between a screw and a bolt?

A: A screw is a threaded fastener that is used to hold objects together or to exert a clamping force, while a bolt is a threaded fastener that is used to hold objects together by passing through a hole in one object and screwing into a threaded hole in another object.

## Q: What is the difference between a spring and a damper?

A: A spring is a mechanical component that stores and releases elastic potential energy in response to a deformation, while a damper is a mechanical component that dissipates kinetic energy by converting it into heat, usually through fluid resistance.

## Q: What is the difference between a servo motor and a stepper motor?

A: A servo motor is a motor that rotates to a precise position or angle, based on an input signal, while a stepper motor is a motor that rotates in small, incremental steps, based on a series of input pulses.

## Q: What is the difference between a control system and an automation system?

A: A control system is a system that regulates the behavior of a physical process or system, usually by manipulating inputs or outputs, while an automation system is a system that performs tasks automatically, without human intervention, usually through the use of sensors, actuators, and control algorithms.

## Q: What is the difference between a sensor and an actuator?

A: A sensor is a device that detects or measures a physical quantity, such as temperature or pressure, and converts it into an electrical signal, while an actuator is a device that converts an electrical or mechanical signal into a physical action, such as movement or force.

## Q: What is the difference between a circuit and a network?

A: A circuit is a closed path that allows electrical current to flow, usually consisting of a power source, a load, and a series of conductive elements, such as wires and resistors, while a network is a collection of interconnected circuits or components, usually with a specific function or purpose.

## Q: What is the difference between AC and DC voltage?

A: AC voltage is an alternating voltage that changes direction and magnitude periodically, while DC voltage is a direct voltage that maintains a constant polarity and magnitude.

## Q: What is the difference between a transformer and an inductor?

A: A transformer is a device that transfers electrical energy from one circuit to another through electromagnetic induction, while an inductor is a passive electrical component that stores energy in a magnetic field.

## Q: What is the difference between a capacitor and a battery?

A: A capacitor is a passive electrical component that stores energy in an electric field, while a battery is an electrochemical device that converts chemical energy into electrical energy and stores it for later use.

## Q: What is the difference between an analog signal and a digital signal?

A: An analog signal is a continuous signal that varies over time, while a digital signal is a discrete signal that consists of a series of binary values (0s and 1s).

## Q: What is the difference between a microcontroller and a microprocessor?

A: A microcontroller is a compact integrated circuit that contains a processor, memory, and I/O peripherals, and is designed to control a specific function or device, while a microprocessor is a general-purpose processing unit that requires external memory and peripherals to function.

## Q: What is the difference between a field-effect transistor (FET) and a bipolar junction transistor (BJT)?

A: An FET is a type of transistor that uses an electric field to control the flow of current, while a BJT is a type of transistor that uses the interaction of two different types of semiconductor material to control the flow of current.

## Q: What is the difference between a breadboard and a PCB?

A: A breadboard is a prototyping tool that allows electronic components to be easily interconnected without the need for soldering, while a PCB (printed circuit board) is a permanent board that contains a circuit layout and is used for mass production of electronic devices.

## Q: What is the difference between an encoder and a decoder?

A: An encoder is a device that converts a signal or data into a specific code or format, while a decoder is a device that converts a code or format into the original signal or data.

## Q: What is the difference between a logic gate and a flip-flop?

A: A logic gate is an electronic circuit that performs a Boolean function, such as AND, OR, or NOT, while a flip-flop is a bistable circuit that can be in one of two stable states, usually used for storing data.

## Q: What is the difference between an op-amp and a comparator?

A: An op-amp (operational amplifier) is an electronic circuit that amplifies the difference between two input voltages, while a comparator is an electronic circuit that compares two input voltages and produces a digital output based on their relative magnitudes.

## Q: What is the difference between an oscillator and a resonator?

A: An oscillator is an electronic circuit that generates a periodic signal or waveform, while a resonator is a passive component that stores energy in a resonant frequency or mode.

## Q: What is the difference between a multiplexer and a demultiplexer?

A: A multiplexer is an electronic circuit that selects one of several input signals and forwards it to a single output, while a demultiplexer is an electronic circuit that takes a single input signal and forwards it to one of several output channels.

## Q: What is the difference between a motor and a generator?

A: A motor is an electrical device that converts electrical energy into mechanical energy, usually by rotating a shaft, while a generator is an electrical device that converts mechanical energy into electrical energy, usually by rotating a shaft.

## Q: What is the difference between a thermocouple and a thermistor?

A: A thermocouple is a type of temperature sensor that uses the voltage produced by two different metals to measure temperature, while a thermistor is a type of temperature sensor that uses the change in resistance of a semiconductor material to measure temperature.

## Q: What is the difference between a strain gauge and a load cell?

A: A strain gauge is a type of sensor that measures strain or deformation in a material by measuring the change in resistance, while a load cell is a type of transducer that measures the force applied to it and converts it into an electrical signal.

## Q: What is the difference between a pulse width modulation (PWM) signal and a frequency modulation (FM) signal?

A: A PWM signal is a type of digital signal that varies the duty cycle of a square wave to control the power delivered to a load, while an FM signal is a type of analog signal that varies the frequency of a carrier wave to encode information.

## Q: What is the difference between a relay and a transistor?

A: A relay is an electromagnetic switch that uses a coil to control the opening and closing of a set of contacts, while a transistor is an electronic switch that uses the biasing of a semiconductor to control the flow of current.

## Q: What is the difference between a hydraulic system and a pneumatic system?

A: A hydraulic system uses pressurized fluid, usually oil, to transmit power and control motion, while a pneumatic system uses pressurized gas, usually air, to transmit power and control motion.

## Q: What is the difference between a centrifugal pump and a positive displacement pump?

A: A centrifugal pump uses a rotating impeller to create a flow of fluid through centrifugal force, while a positive displacement pump uses a set of reciprocating or rotating elements to displace a fixed volume of fluid with each stroke.

## Q: What is the difference between a closed-loop system and an open-loop system?

A: A closed-loop system uses feedback to adjust the output based on the input and desired response, while an open-loop system does not use feedback and produces a fixed output regardless of the input.

## Q: What is the difference between a stepper motor and a servo motor?

A: A stepper motor is a type of motor that rotates in small, precise steps, while a servo motor is a type of motor that rotates to a specific position based on the input signal.

## Q: What is the difference between a vector and a scalar?

A: A vector is a quantity that has both magnitude and direction, while a scalar is a quantity that has only magnitude.

## Q: What is the difference between a force and a moment?

A: A force is a push or pull on an object, while a moment is the rotational effect of a force around an axis or pivot point.

## Q: What is the difference between a static and dynamic load?

A: A static load is a load that remains stationary or is applied slowly, while a dynamic load is a load that changes rapidly or is applied with motion.

## Q: What is the difference between stress and strain?

A: Stress is the force per unit area applied to a material, while strain is the resulting deformation or change in shape of the material.

## Q: What is the difference between bending and torsion?

A: Bending is the deformation of a material due to a transverse load or force applied perpendicular to the length of the material, while torsion is the deformation of a material due to a twisting or torque force applied around the length of the material.

## Q: What is the difference between a truss and a beam?

A: A truss is a structure made up of interconnected triangles that can support loads in tension and compression, while a beam is a structural element that supports loads primarily in bending.

## Q: What is the difference between a bearing and a bushing?

A: A bearing is a type of machine element that supports or guides rotating or sliding shafts or components, while a bushing is a type of bearing that supports or guides rotating or sliding shafts or components with a cylindrical or sleeve-shaped component.

## Q: What is the difference between a cantilever beam and a simply supported beam?

A: A cantilever beam is a beam that is fixed at one end and free at the other, while a simply supported beam is a beam that is supported at both ends and free to rotate.

## Q: What is the difference between compression and tension?

A: Compression is a force that squeezes or presses a material, while tension is a force that stretches or pulls a material.

## Q: What is the difference between kinematics and kinetics?

A: Kinematics is the study of the motion of objects without consideration of the forces that cause the motion, while kinetics is the study of the forces that cause motion.

## Q: What is the difference between elastic and plastic deformation?

A: Elastic deformation is the temporary deformation of a material that returns to its original shape when the force is removed, while plastic deformation is the permanent deformation of a material that does not return to its original shape when the force is removed.

## Q: What is the difference between an amplifier and an attenuator?

A: An amplifier is an electronic device that increases the amplitude of a signal, while an attenuator is an electronic device that reduces the amplitude of a signal.

## Q: What is the difference between a cathode and an anode?

A: A cathode is the electrode of an electrochemical cell or electronic device that is negatively charged and attracts positive ions, while an anode is the electrode that is positively charged and attracts negative ions.

## Q: What is the difference between a capacitor and an inductor?

A: A capacitor is an electronic component that stores electrical charge, while an inductor is an electronic component that stores electrical energy in a magnetic field.

## Q: What is the difference between an AC and DC circuit?

A: An AC circuit is a circuit that uses alternating current, where the voltage and current periodically change direction, while a DC circuit is a circuit that uses direct current, where the voltage and current flow in one direction.

## Q: What is the difference between a conductor and an insulator?

A: A conductor is a material that allows electrical current to flow easily, while an insulator is a material that does not allow electrical current to flow easily.

## Q: What is the difference between a resistor and a capacitor?

A: A resistor is an electronic component that limits the flow of current in a circuit, while a capacitor is an electronic component that stores electrical charge.

## Q: What is the difference between a motor and a generator?

A: A motor converts electrical energy into mechanical energy, while a generator converts mechanical energy into electrical energy.

## Q: What is the difference between a synchronous motor and an induction motor?

A: A synchronous motor operates at a fixed speed that is synchronized with the frequency of the electrical supply, while an induction motor operates at a speed slightly less than the frequency of the electrical supply.

## Q: What is the difference between a feedback control system and a feedforward control system?

A: A feedback control system uses feedback from the output to adjust the input and maintain a desired response, while a feedforward control system anticipates disturbances and adjusts the input to maintain a desired response.

## Q: What is the difference between a closed-loop control system and an open-loop control system?

A: A closed-loop control system uses feedback to adjust the input based on the output and maintain a desired response, while an open-loop control system does not use feedback and produces a fixed output regardless of the input or output.

## Q: What is the difference between a ladder logic diagram and a control flow diagram?

A: A ladder logic diagram is a graphical programming language used for programmable logic controllers (PLCs), while a control flow diagram is a graphical representation of the flow of a program or algorithm.

## Q: What is the difference between an actuator and a sensor?

A: An actuator is a device that converts electrical, hydraulic, or pneumatic energy into mechanical motion, while a sensor is a device that detects or measures a physical quantity and converts it into an electrical signal.

## Q: What is the difference between a heat engine and a heat pump?

A: A heat engine converts heat energy into mechanical energy, while a heat pump transfers heat energy from a cooler space to a warmer space.

## Q: What is the difference between a rankine cycle and a brayton cycle?

A: A rankine cycle is a thermodynamic cycle used in steam power plants, while a brayton cycle is a thermodynamic cycle used in gas turbine engines.

## Q: What is the difference between a thermometer and a thermocouple?

A: A thermometer is a device used to measure temperature using a liquid, gas, or electrical resistance, while a thermocouple is a device used to measure temperature based on the voltage generated by the junction of two dissimilar metals.

## Q: What is the difference between a diode and a transistor?

A: A diode is a semiconductor device that allows current to flow in only one direction, while a transistor is a semiconductor device that can amplify or switch electronic signals.

## Q: What is the difference between a microcontroller and a microprocessor?

A: A microcontroller is a self-contained computer on a single integrated circuit that is designed for embedded systems, while a microprocessor is a general-purpose computer processor used in a wide range of computing applications.

## Q: What is the difference between a digital signal and an analog signal?

A: A digital signal is a discrete signal that can only take on specific values, while an analog signal is a continuous signal that can take on any value within a range.

## Q: What is the difference between a frequency and a wavelength?

A: Frequency is the number of cycles per second of a waveform, while wavelength is the distance between two corresponding points on a waveform.

## Q: What is the difference between a transistor and a thyristor?

A: A transistor is a semiconductor device that can amplify or switch electronic signals, while a thyristor is a semiconductor device that acts as a switch, allowing current to flow in only one direction.

## Q: What is the difference between a relay and a contactor?

A: A relay is an electromagnetic switch used for low-power control signals, while a contactor is an electromagnetic switch used for high-power control signals.

## Q: What is the difference between a pressure sensor and a force sensor?

A: A pressure sensor measures pressure, which is the amount of force per unit area, while a force sensor measures force directly.

## Q: What is the difference between a strain gauge and a load cell?

A: A strain gauge measures the strain or deformation of an object, while a load cell measures the force applied to an object.

## Q: What is the difference between an encoder and a resolver?

A: An encoder is a device used to convert linear or rotational motion into an electrical signal, while a resolver is a device used to measure the angle of rotation of a shaft or motor.