# Engineering Mechanics Viva Questions and Answers

Contents

## What is meant by mechanics?

Mechanics is the branch of physics that deals with the study of motion, forces, and energy. It is concerned with how objects move and how forces affect them.

## What is meant by statics?

Statics is the branch of mechanics that deals with the study of forces in equilibrium. It is concerned with the analysis of forces acting on stationary objects or systems.

## What is meant by dynamics?

Dynamics is the branch of mechanics that deals with the study of motion and the forces that cause it. It is concerned with the analysis of forces acting on moving objects or systems.

## What is meant by force?

Force is an influence that causes an object to undergo a change in motion, either by accelerating it or by causing it to deform. Force is measured in units of Newtons (N).

## What is meant by moment of a force?

Moment of a force is a measure of the tendency of a force to cause rotational motion about an axis. It is the product of the force and the perpendicular distance from the axis of rotation to the line of action of the force. It is measured in units of Newton-meters (Nm).

## What is meant by moment of inertia?

Moment of inertia is a measure of an object’s resistance to rotational motion. It is the sum of the products of each particle’s mass and the square of its distance from the axis of rotation. It is measured in units of kilogram-meters squared (kg-m^2).

## What is meant by work?

Work is the product of the force applied to an object and the distance the object moves in the direction of the force. It is measured in units of Joules (J).

## What is meant by power?

Power is the rate at which work is done. It is the product of the force applied to an object, the distance the object moves in the direction of the force, and the time it takes to do the work. It is measured in units of Watts (W).

## What is meant by energy?

Energy is the ability of a system to do work. It exists in different forms such as kinetic, potential, thermal, electrical, and chemical. It is measured in units of Joules (J).

## What is meant by conservation of energy?

Conservation of energy is a fundamental principle in physics that states that energy cannot be created or destroyed, only transferred or converted from one form to another. The total amount of energy in a closed system remains constant.

## What is meant by center of gravity?

Center of gravity is the point in an object or a system where the weight can be considered to be concentrated, and the object or system will balance perfectly. It is the point where the gravitational force on an object is equal in all directions.

## What is meant by the moment of a couple?

A couple is a pair of forces that are equal in magnitude but opposite in direction, and that act on different points of an object or a system. The moment of a couple is the product of one of the forces and the perpendicular distance between the forces.

## What is meant by the principle of virtual work?

The principle of virtual work is a fundamental principle in mechanics that states that if a system is in equilibrium, the work done by the internal forces and the work done by the external forces must balance each other.

## What is meant by the principle of superposition?

The principle of superposition states that the net effect of several forces acting on an object is the same as the effect of each individual force acting alone.

## What is meant by the principle of moments?

The principle of moments states that for a system in equilibrium, the sum of the clockwise moments about any point must be equal to the sum of the counterclockwise moments about the same point.

## What is meant by friction?

Friction is the force that opposes motion between two surfaces that are in contact. It arises due to the roughness of the surfaces, and it is proportional to the normal force between the surfaces.

## What is meant by coefficient of friction?

Coefficient of friction is a dimensionless quantity that represents the ratio of the frictional force to the normal force between two surfaces in contact. It depends on the nature of the surfaces and the conditions under which they are in contact.

## What is meant by Newton’s laws of motion?

Newton’s laws of motion are three fundamental laws that describe the behavior of objects in motion. The first law states that an object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity, unless acted upon by a net external force. The second law states that the acceleration of an object is directly proportional to the net external force acting on it, and inversely proportional to its mass. The third law states that for every action, there is an equal and opposite reaction.

## What is meant by impulse?

Impulse is the change in momentum of an object caused by a force acting on it for a specific period of time. It is the product of the force and the time for which it acts, and it is measured in units of Newton-seconds (Ns).

## What is meant by momentum?

Momentum is the product of an object’s mass and velocity. It is a vector quantity, and its direction is the same as the direction of the object’s velocity. The total momentum of a closed system is conserved, meaning that the total momentum before a collision or an interaction is equal to the total momentum after the collision or interaction.

## What is meant by elasticity?

Elasticity is the property of a material that allows it to return to its original shape and size after it has been deformed by an external force. The degree of elasticity depends on the type of material and the magnitude of the force.

## What is meant by Hooke’s law?

Hooke’s law states that the deformation of an elastic material is proportional to the force applied to it. Mathematically, it is expressed as F = kx, where F is the force applied, x is the deformation, and k is the spring constant.

## What is meant by stress?

Stress is the force per unit area applied to a material that causes it to deform. It is measured in units of Pascals (Pa).

## What is meant by strain?

Strain is the amount of deformation per unit length that occurs in a material when it is subjected to stress. It is a dimensionless quantity.

## What is meant by Young’s modulus?

Young’s modulus is a measure of the stiffness of a material. It is the ratio of the stress applied to a material to the strain produced in the material. It is measured in units of Pascals (Pa).

## What is meant by shear stress?

Shear stress is the stress that occurs when two forces act parallel to each other, but in opposite directions, on a surface or a material. It is measured in units of Pascals (Pa).

## What is meant by torsion?

Torsion is the twisting of an object due to the application of a torque or a twisting force. It can cause deformation or failure of the object if the torque is too high.

## What is meant by bending stress?

Bending stress is the stress that occurs when a beam or a plate is subjected to a bending moment or a force that causes it to bend. It is proportional to the distance from the neutral axis of the beam or plate.

## What is meant by fatigue failure?

Fatigue failure is a type of failure that occurs in materials when they are subjected to repeated loading and unloading cycles. It can cause cracks to form and propagate, eventually leading to failure of the material.

## What is meant by creep?

Creep is the slow, time-dependent deformation of a material when it is subjected to a constant load or stress over a long period of time. It is a common phenomenon in high-temperature applications.

## What is meant by a beam?

A beam is a structural element that is designed to resist bending and shear forces. It is typically a long, slender member that is supported at its ends and is loaded along its length.

## What is meant by a truss?

A truss is a structure composed of straight members connected at their ends by joints. Trusses are used to support roofs, bridges, and other structures.

## What is meant by a frame?

A frame is a structure composed of straight members connected at their ends by joints, and it is designed to support loads in all directions. Frames are commonly used in buildings and other structures.

## What is meant by a centroid?

The centroid is the geometric center of an object or a system. It is the point where the area or volume is evenly distributed around it.

## What is meant by the Euler-Bernoulli beam theory?

The Euler-Bernoulli beam theory is a mathematical model that describes the behavior of a beam under bending. It assumes that the beam is slender and that the deformation is small, and it uses the principles of mechanics and calculus to calculate the deflection and stress in the beam.

## What is meant by the Navier-Stokes equations?

The Navier-Stokes equations are a set of partial differential equations that describe the motion of fluids. They are used in fluid mechanics to analyze the behavior of fluids under different conditions, such as viscosity, pressure, and flow rate.

## What is meant by a rigid body?

A rigid body is a body that does not deform under the action of external forces. It is an idealized concept used in mechanics to simplify the analysis of motion.

## What is meant by a moment?

Moment is a measure of the tendency of a force to rotate an object around an axis. It is the product of the force and the perpendicular distance from the axis to the line of action of the force.

## What is meant by the principle of work and energy?

The principle of work and energy states that the work done by the net external forces on a system is equal to the change in the system’s kinetic energy. It is a useful tool in mechanics for calculating the motion of objects and systems.

## What is meant by friction?

Friction is the force that resists motion between two surfaces that are in contact with each other. It is caused by the irregularities on the surfaces that interlock and resist relative motion.

## What is meant by a free body diagram?

A free body diagram is a graphical representation of the forces acting on a body or an object. It is used in mechanics to analyze the motion of objects and to calculate the forces acting on them.

## What is meant by a moment of a force?

The moment of a force is a measure of its tendency to cause rotational motion. It is the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation.

## What is meant by a couple?

A couple is a pair of forces that are equal in magnitude, opposite in direction, and parallel to each other. They produce a torque or a moment that tends to rotate an object around an axis.

## What is meant by a center of gravity?

The center of gravity is the point where the weight of an object is concentrated or balanced. It is the point where the object can be supported without tipping over or rotating.

## What is meant by a moment of a couple?

The moment of a couple is a measure of its tendency to cause rotational motion. It is the product of one of the forces and the perpendicular distance between the two forces.

## What is meant by the law of conservation of momentum?

The law of conservation of momentum states that the total momentum of a system of objects is conserved, provided that no external forces act on the system. It is a fundamental law of physics that applies to all objects, including those in mechanics.

## What is meant by the principle of virtual work?

The principle of virtual work states that the work done by the internal forces in a system of connected bodies is equal to the work done by the external forces acting on the system. It is a powerful tool in mechanics for analyzing the behavior of systems under different conditions.

## What is meant by a distributed load?

A distributed load is a load that is spread over a surface or a volume rather than concentrated at a single point. It is commonly encountered in mechanics in the form of pressure, weight, or force per unit area.

## What is meant by a point load?

A point load is a load that is applied at a single point or location. It is commonly encountered in mechanics in the form of a concentrated force or weight.

## What is meant by stress?

Stress is the force per unit area acting on a material. It is a measure of the internal resistance of a material to deformation under the action of external forces.

## What is meant by strain?

Strain is the measure of the deformation of a material under the action of stress. It is a measure of the change in the shape or size of a material due to the application of external forces.

## What is meant by elasticity?

Elasticity is the ability of a material to recover its original shape and size after deformation under the action of stress. It is a property of materials that determines their resistance to deformation and their ability to return to their original shape.

## What is meant by plasticity?

Plasticity is the ability of a material to undergo permanent deformation under the action of stress. It is a property of materials that determines their ability to withstand deformation beyond their elastic limit.

## What is meant by Hooke’s law?

Hooke’s law states that the stress applied to a material is proportional to the strain produced in the material, provided that the material remains within its elastic limit. It is a fundamental law of mechanics that applies to many materials, including metals, plastics, and elastomers.

## What is meant by the yield strength of a material?

The yield strength of a material is the stress at which the material begins to undergo permanent deformation. It is an important property of materials that determines their ability to withstand loads without undergoing plastic deformation.

## What is meant by the ultimate strength of a material?

The ultimate strength of a material is the maximum stress that the material can withstand before it fails or fractures. It is an important property of materials that determines their ability to withstand extreme loads without breaking or collapsing.

## What is meant by the factor of safety?

The factor of safety is the ratio of the maximum stress that a material can withstand to the maximum stress that is expected to be applied to the material. It is used in engineering to ensure that a structure or a component is safe and reliable under all expected conditions.

## What is meant by the failure mode of a material?

The failure mode of a material is the manner in which the material fails or fractures under the action of stress. It can be brittle, ductile, or a combination of both, and it depends on the properties of the material and the type of stress applied to it.

## What is meant by the principle of superposition?

The principle of superposition states that the response of a linear system to a combination of loads can be obtained by adding the responses of the system to each individual load. It is a powerful tool in mechanics for analyzing the behavior of complex systems under different conditions.

## What is meant by the moment of inertia?

The moment of inertia is a measure of the resistance of a body to rotational motion. It is the sum of the products of the mass of each particle in the body and the square of its distance from the axis of rotation.

## What is meant by the radius of gyration?

The radius of gyration is a measure of the distribution of mass in a body about its axis of rotation. It is the square root of the ratio of the moment of inertia to the total mass of the body.

## What is meant by the parallel axis theorem?

The parallel axis theorem states that the moment of inertia of a body about an axis parallel to its centroidal axis is equal to the sum of the moment of inertia about the centroidal axis and the product of the total mass of the body and the square of the distance between the two axes.

## What is meant by the perpendicular axis theorem?

The perpendicular axis theorem states that the moment of inertia of a plane figure about an axis perpendicular to its plane is equal to the sum of the moments of inertia of the figure about two perpendicular axes in its plane.

## What is meant by the center of percussion?

The center of percussion is the point on a rigid body where a blow delivered to the body will produce no reaction at the point of support. It is the point where the impact force acts as if it were concentrated, resulting in a purely rotational motion of the body.

## What is meant by the moment of a couple?

The moment of a couple is a measure of the rotational effect of two equal and opposite forces acting on a rigid body at different points. It is equal to the product of one of the forces and the perpendicular distance between the two forces.

## What is meant by the principle of conservation of energy?

The principle of conservation of energy states that the total energy of a system is conserved, provided that no external forces act on the system. It is a fundamental law of physics that applies to all objects and processes, including those in mechanics.

## What is meant by the principle of work and energy?

The principle of work and energy states that the work done by external forces on a system is equal to the change in the kinetic energy of the system. It is a powerful tool in mechanics for analyzing the motion of objects and the forces acting on them.

## What is meant by the principle of impulse and momentum?

The principle of impulse and momentum states that the impulse applied to a system is equal to the change in momentum of the system. It is a fundamental law of physics that applies to all objects and processes, including those in mechanics.

## What is meant by the concept of rigid body?

A rigid body is a body that maintains its shape and size under the action of external forces. It is an idealized model used in mechanics to simplify the analysis of motion and forces acting on objects.

## What is the difference between statics and dynamics?

Statics deals with the analysis of bodies in equilibrium under the action of forces, while dynamics deals with the analysis of bodies in motion under the action of forces.

## What is meant by the free body diagram?

A free body diagram is a graphical representation of a body or system that shows all the forces acting on it. It is a powerful tool used in mechanics to simplify the analysis of forces and motion.

## What is meant by the principle of virtual work?

The principle of virtual work states that the work done by a set of forces in a system is equal to zero if the system is in equilibrium. It is a fundamental principle in mechanics that is used to analyze the behavior of structures and machines.

## What is meant by the law of motion?

The laws of motion are a set of fundamental principles in physics that describe the behavior of objects in motion. They were formulated by Sir Isaac Newton and are the foundation of classical mechanics.

## What is meant by the first law of motion?

The first law of motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue in motion with a constant velocity, unless acted upon by an external force.

## What is meant by the second law of motion?

The second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This law is also known as the law of force and acceleration.

## What is meant by the third law of motion?

The third law of motion states that for every action, there is an equal and opposite reaction. This law is also known as the law of action and reaction.

## What is meant by the impulse of a force?

The impulse of a force is the product of the force and the time for which it acts. It is a measure of the change in momentum of an object due to the force.

## What is meant by the coefficient of restitution?

The coefficient of restitution is a measure of the elasticity of a collision between two objects. It is defined as the ratio of the relative velocity of separation to the relative velocity of approach.

## What is meant by the principle of superposition?

The principle of superposition states that the net effect of two or more forces acting on a body is the vector sum of their individual effects. It is a powerful tool used in mechanics to simplify the analysis of complex systems.

## What is meant by the center of mass?

The center of mass is a point in a body or system where the entire mass of the body or system is concentrated. It is the point where the net force acting on the body or system is considered to act.

## What is the difference between the center of mass and the centroid?

The center of mass is a point where the entire mass of a body or system is concentrated, whereas the centroid is a point that represents the geometric center of a shape or object. In a uniform object, the center of mass and centroid coincide.

## What is meant by the moment of inertia?

The moment of inertia is a measure of a body’s resistance to rotational motion. It is defined as the sum of the products of the mass of each particle in a body and the square of its distance from the axis of rotation.

## What is meant by torque?

Torque is the measure of the force that causes an object to rotate around an axis or pivot point. It is defined as the product of the force and the perpendicular distance from the axis of rotation to the line of action of the force.

## What is meant by the principle of conservation of angular momentum?

The principle of conservation of angular momentum states that the total angular momentum of a system remains constant if there are no external torques acting on the system. It is a fundamental principle in mechanics that is used to analyze the behavior of rotating systems.

## What is meant by the principle of work and energy?

The principle of work and energy states that the work done on a system is equal to the change in its kinetic energy. It is a fundamental principle in mechanics that is used to analyze the behavior of mechanical systems.

## What is meant by the principle of conservation of energy?

The principle of conservation of energy states that energy cannot be created or destroyed, but it can be transformed from one form to another. It is a fundamental principle in physics that is used to analyze the behavior of physical systems.

## What is meant by the principle of virtual displacement?

The principle of virtual displacement states that the virtual work done by a set of forces is equal to zero if the displacement of the system is infinitesimal. It is a fundamental principle in mechanics that is used to analyze the behavior of structures and machines.

## What is meant by the principle of minimum potential energy?

The principle of minimum potential energy states that a system will be in equilibrium when its potential energy is minimum. It is a fundamental principle in mechanics that is used to analyze the behavior of structures and machines.

## What is the difference between statics and dynamics?

Statics deals with the study of bodies at rest or in a state of equilibrium, whereas dynamics deals with the study of bodies in motion and the forces that cause them to move.

## What is meant by the principle of superposition?

The principle of superposition states that the net effect of two or more forces acting on a body is equal to the algebraic sum of the individual effects of each force acting alone.

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

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

## What is the difference between a conservative and a non-conservative force?

A conservative force is a force that does not depend on the path taken by an object, and the work done by the force is independent of the path taken. A non-conservative force, on the other hand, depends on the path taken by an object, and the work done by the force is not independent of the path taken.

## What is meant by the principle of equilibrium?

The principle of equilibrium states that for a body to be in a state of equilibrium, the sum of the forces acting on the body must be zero, and the sum of the moments about any point must also be zero.

## What is meant by the principle of virtual work?

The principle of virtual work states that the work done by a set of forces on a system is equal to the change in the potential energy of the system. It is a fundamental principle in mechanics that is used to analyze the behavior of structures and machines.

## What is meant by the principle of impulse and momentum?

The principle of impulse and momentum states that the impulse on a body is equal to the change in its momentum. It is a fundamental principle in mechanics that is used to analyze the behavior of objects in motion.

## What is meant by the principle of action and reaction?

The principle of action and reaction states that for every action, there is an equal and opposite reaction. It is a fundamental principle in mechanics that is used to analyze the behavior of objects in motion.

## What is the difference between linear and angular momentum?

Linear momentum is the product of the mass and velocity of an object, while angular momentum is the product of the moment of inertia and the angular velocity of an object.

## What is meant by the principle of moments?

The principle of moments states that the sum of the moments about any point in a system in equilibrium is zero. It is a fundamental principle in mechanics that is used to analyze the behavior of structures and machines.

## What is the difference between stress and strain?

Stress is the internal force per unit area that resists the deformation of a body, while strain is the measure of deformation caused by stress.

## What is meant by the elastic limit of a material?

The elastic limit of a material is the maximum stress that a material can sustain without undergoing permanent deformation.

## What is meant by the Poisson’s ratio of a material?

The Poisson’s ratio of a material is the ratio of the transverse strain to the axial strain when a material is subjected to an axial stress.

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

A beam is a structural element that is designed to carry loads perpendicular to its longitudinal axis, while a column is a structural element that is designed to carry loads primarily in the axial direction.

## What is meant by the shear force and bending moment in a beam?

The shear force in a beam is the force that acts perpendicular to the longitudinal axis of the beam and tends to shear the beam, while the bending moment in a beam is the moment that acts perpendicular to the longitudinal axis of the beam and tends to bend the beam.

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

A statically determinate structure is one in which the forces can be determined using only the equations of equilibrium, while a statically indeterminate structure is one in which the forces cannot be determined using only the equations of equilibrium.

## What is meant by the moment of inertia of a body?

The moment of inertia of a body is the measure of the body’s resistance to rotational motion, and it depends on the mass distribution of the body and the axis of rotation.

## What is meant by the center of gravity of a body?

The center of gravity of a body is the point at which the entire weight of the body can be considered to act when the body is in a uniform gravitational field.

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

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

## What is meant by the principle of work and energy?

The principle of work and energy states that the work done by the external forces acting on a system is equal to the change in the system’s kinetic energy.

## What is the difference between internal and external forces?

Internal forces are the forces that act within a body or system, while external forces are the forces that act on a body or system from the outside.

## What is meant by the principle of conservation of energy?

The principle of conservation of energy states that the total energy of an isolated system remains constant, that is, energy cannot be created or destroyed but only transformed from one form to another.

## What is meant by the principle of conservation of momentum?

The principle of conservation of momentum states that the total momentum of an isolated system remains constant, that is, the momentum of a system cannot be created or destroyed but only transferred from one object to another within the system.

## What is meant by the principle of virtual displacement?

The principle of virtual displacement states that the work done by all the external forces acting on a system during a virtual displacement is equal to zero.

## What is meant by the principle of least action?

The principle of least action, also known as Hamilton’s principle, states that the path taken by a system between two points in space and time is the one that minimizes the action integral, which is a function of the system’s kinetic and potential energies.

## What is meant by the principle of least work?

The principle of least work states that the actual path taken by a system between two points in space and time is the one that minimizes the total work done by the system.

## What is meant by the principle of minimum potential energy?

The principle of minimum potential energy states that a system in stable equilibrium will assume the configuration that minimizes its potential energy.

## What is meant by the principle of maximum entropy?

The principle of maximum entropy states that a system will naturally evolve towards a state of maximum disorder or randomness.

## What is meant by the principle of maximum work?

The principle of maximum work states that a system will evolve towards the state that maximizes the work it can perform.