Engineering Mechanics Viva Questions and Answers
Q: What is meant by engineering mechanics?
A: Engineering mechanics is the branch of engineering that deals with the study of forces and their effects on bodies in motion or at rest.
Q: What are the different types of forces?
A: The different types of forces are: gravitational force, electromagnetic force, nuclear force, frictional force, tension force, and compression force.
Q: What is a free body diagram?
A: A free body diagram is a sketch that shows the external forces acting on an object.
Q: What is meant by the principle of equilibrium?
A: The principle of equilibrium states that the net force acting on an object in equilibrium is zero.
Q: What is a couple?
A: A couple is a pair of forces that are equal in magnitude, opposite in direction, and parallel to each other but do not act along the same line.
Q: What is meant by the moment of a force?
A: The moment of a force is the product of the force and the perpendicular distance between the line of action of the force and the point about which the moment is taken.
Q: What is meant by the centroid of an area?
A: The centroid of an area is the point at which the entire area can be assumed to be concentrated for the purpose of analysis.
What is meant by the term ‘mechanics’?
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effect of these bodies on their environment.
What are the three laws of motion?
The three laws of motion, as stated by Sir Isaac Newton, are:

Every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.

The rate of change of momentum of an object is directly proportional to the force applied, and takes place in the direction in which the force is applied.

For every action, there is an equal and opposite reaction.
What is the difference between a scalar and a vector quantity?
Scalar quantities have only magnitude, while vector quantities have both magnitude and direction. Examples of scalar quantities include mass, time, and temperature, while examples of vector quantities include velocity, acceleration, and force.
What is the principle of virtual work?
The principle of virtual work states that the work done by a set of forces on a rigid body is zero if the body is in equilibrium. This principle is used to solve problems involving the equilibrium of a system of forces.
What is Hooke’s Law?
Hooke’s Law states that the force required to extend or compress a spring is directly proportional to the extension or compression of the spring, provided that the limit of proportionality is not exceeded. This law is used to calculate the elastic deformation of materials.
What is the difference between stress and strain?
Stress is the force per unit area that a material experiences, while strain is the deformation of a material in response to stress. Stress is a measure of the internal forces within a material, while strain is a measure of the external response of the material to those forces.
What is the difference between static and dynamic friction?
Static friction is the frictional force that must be overcome to set an object in motion, while dynamic friction is the frictional force that opposes the motion of an object that is already in motion.
What is the difference between impulse and momentum?
Momentum is the product of an object’s mass and velocity, while impulse is the change in momentum that occurs when a force is applied to an object for a period of time. Impulse is equal to the force applied multiplied by the time for which it is applied.
What is the principle of conservation of energy?
The principle of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. This principle is used to analyze the behavior of systems that involve the transfer of energy, such as collisions and mechanical systems.
What is the center of gravity?
The center of gravity is the point in a body or system where the force of gravity can be considered to act. It is the point at which the weight of the body is evenly distributed in all directions.
What is the difference between a moment and a couple?
A moment is a force that is applied at a distance from a pivot point, causing a rotational motion. A couple is a pair of equal and opposite forces that act parallel to each other, but do not have a single pivot point. A couple produces a pure rotational motion.
What is the difference between a beam and a truss?
A beam is a structural element that is designed to support a load by bending. It typically has a long, slender shape and is made of a single material, such as steel or wood. A truss, on the other hand, is a framework made of interconnected triangles. It is designed to support a load by distributing it across the entire structure.
What is the difference between a statically determinate and a statically indeterminate structure?
A statically determinate structure is one in which the reactions and internal forces can be calculated using the equations of static equilibrium alone. A statically indeterminate structure is one in which additional equations are required to calculate the reactions and internal forces.
What is the difference between a kinematic and a kinetic analysis?
A kinematic analysis is concerned with the motion of objects without consideration of the forces that cause the motion. A kinetic analysis, on the other hand, considers the forces that cause motion and their effect on the motion of objects.
What is the difference between a rigid body and a deformable body?
A rigid body is one that does not deform when subjected to external forces, while a deformable body is one that does deform. The behavior of a rigid body can be analyzed using the equations of statics and dynamics, while the behavior of a deformable body requires additional considerations such as stress and strain.
What is a moment of inertia?
The moment of inertia is a measure of the resistance of an object to rotational motion. It is the sum of the products of the mass of each particle in the object and the square of its distance from a given axis.
What is the difference between a kinematic and kinetic problem in mechanics?
A kinematic problem involves determining the motion of an object without considering the forces causing the motion. A kinetic problem, on the other hand, involves determining the motion of an object by considering the forces causing the motion.
What is the difference between a rigid body and a deformable body?
A rigid body is a body that does not deform under the action of external forces, while a deformable body is a body that does deform under the action of external forces.
What is a moment of a force?
The moment of a force, also known as torque, is the tendency of a force to cause rotational motion about a pivot point. It is equal to the magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot point.
What is the difference between center of mass and center of gravity?
The center of mass is the point at which the mass of an object is concentrated, while the center of gravity is the point at which the weight of an object is concentrated. In most cases, the center of mass and center of gravity are the same point, but this is not always true in situations where there is a nonuniform gravitational field.
What is the principle of work and energy?
The principle of work and energy states that the work done by the net force on an object is equal to the change in the object’s kinetic energy. This principle is used to analyze the motion of systems that involve the transfer of energy, such as collisions and mechanical systems.
What is the difference between a conservative and nonconservative force?
A conservative force is a force that does work that is independent of the path taken, while a nonconservative force is a force that does work that depends on the path taken. Examples of conservative forces include gravity and electrostatic forces, while examples of nonconservative forces include friction and air resistance.
What is the difference between a moment and a couple?
A moment is a force that tends to cause rotation about a single point, while a couple is a pair of equal and opposite forces that tend to cause rotation about an axis perpendicular to the plane containing the forces.
What is a truss?
A truss is a structure composed of interconnected triangles that is used to support loads. Trusses are commonly used in bridges and roofs because of their strength and ability to span long distances.
What is a beam?
A beam is a long, straight structure that is used to support loads. Beams are commonly used in buildings and bridges because of their ability to distribute loads across their length.
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. Cantilever beams are commonly used in buildings and bridges to provide overhangs, while simply supported beams are used to span distances between supports.
What is the difference between stress and strain?
Stress is the internal force per unit area acting on a material, while strain is the deformation of a material resulting from stress. Stress and strain are related by the material’s modulus of elasticity.
What is Hooke’s Law?
Hooke’s Law states that the deformation of a material is directly proportional to the applied force, as long as the deformation is within the material’s elastic limit. This relationship is expressed mathematically as stress = modulus x strain.
What is the difference between tensile stress and compressive stress?
Tensile stress is the stress that results from stretching or pulling a material, while compressive stress is the stress that results from compressing a material. Tensile stress causes the material to elongate, while compressive stress causes the material to shorten.
What is the difference between elastic and plastic deformation?
Elastic deformation is the temporary deformation of a material that disappears when the stress is removed, while plastic deformation is the permanent deformation of a material that remains after the stress is removed.
What is the yield strength of a material?
The yield strength is the stress at which a material begins to deform plastically. It is the point on a stressstrain curve where the material transitions from elastic to plastic deformation.
What is the ultimate strength of a material?
The ultimate strength is the maximum stress that a material can withstand before it fractures or fails.
What is the difference between a statically determinate and indeterminate structure?
A statically determinate structure is one in which the forces can be calculated using equations of static equilibrium, while a statically indeterminate structure is one in which the forces cannot be calculated using equations of static equilibrium alone.
What is the difference between a pin joint and a fixed joint?
A pin joint allows rotation between two connected members, while a fixed joint does not allow any relative movement between two connected members.
What is the difference between a concentrated load and a distributed load?
A concentrated load is a force that is applied at a single point, while a distributed load is a force that is spread out over a larger area or length of a member.
What is the difference between a shear force and a bending moment?
A shear force is a force that acts perpendicular to the longitudinal axis of a member, while a bending moment is a moment that causes the member to bend. Shear forces and bending moments are both important considerations in the design of beams and other structural members.
What is the difference between a statically determinate beam and a statically indeterminate beam?
A statically determinate beam can be analyzed using equations of static equilibrium, while a statically indeterminate beam requires additional analysis using methods such as the flexibility or stiffness method.
What is the difference between a simple beam and a continuous beam?
A simple beam is a beam that is supported at two points, while a continuous beam is a beam that is supported at three or more points. Continuous beams can carry larger loads than simple beams due to the additional support points.
What is the difference between a point load and a uniformly distributed load?
A point load is a force applied at a single point on a structure, while a uniformly distributed load is a load that is spread out evenly over a portion of a structure.
What is the difference between a moment of inertia and a polar moment of inertia?
A moment of inertia is a property of a crosssectional area that describes its resistance to bending, while a polar moment of inertia is a property that describes a crosssectional area’s resistance to torsion.
What is the difference between a free body diagram and an equilibrium equation?
A free body diagram is a diagram that shows all the forces acting on a body, while an equilibrium equation is an equation that describes the balance of forces on a body.
What is the difference between a kinematic chain and a mechanism?
A kinematic chain is a series of interconnected links that transmit motion, while a mechanism is a kinematic chain with at least one driver that provides power to the system.
What is the difference between a spur gear and a helical gear?
A spur gear has teeth that are parallel to the axis of rotation, while a helical gear has teeth that are at an angle to the axis of rotation. Helical gears are more efficient than spur gears due to their increased tooth contact and smoother engagement.
What is the difference between a fluid and a solid?
A fluid is a substance that can flow and take the shape of its container, while a solid has a definite shape and volume.
What is the difference between laminar and turbulent flow?
Laminar flow is a smooth, orderly flow of a fluid, while turbulent flow is a chaotic flow with vortices and eddies. Turbulent flow is typically associated with higher Reynolds numbers.
What is Bernoulli’s principle?
Bernoulli’s principle states that as the velocity of a fluid increases, the pressure decreases. This principle is commonly used to explain the lift generated by airplane wings and the operation of fluid pumps.
What is the difference between a closed system and an open system?
A closed system is a system in which no mass is exchanged with the surroundings, while an open system is a system in which mass can be exchanged with the surroundings.
What is the first law of thermodynamics?
The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another.
What is the second law of thermodynamics?
The second law of thermodynamics states that the total entropy of a system and its surroundings always increases over time.
What is the difference between heat and temperature?
Heat is a form of energy that is transferred between objects due to a temperature difference, while temperature is a measure of the average kinetic energy of the particles in a substance.
What is conduction?
Conduction is the transfer of heat through a material by direct contact between particles.
What is convection?
Convection is the transfer of heat through a fluid (gas or liquid) by the motion of the fluid itself.
What is radiation?
Radiation is the transfer of heat through electromagnetic waves, such as infrared radiation.
What is the difference between a refrigeration cycle and a heat pump cycle?
A refrigeration cycle is a cycle that removes heat from a space and rejects it to a heat sink, while a heat pump cycle is a cycle that absorbs heat from a heat source and delivers it to a space.
What is the difference between a reciprocating engine and a gas turbine engine?
A reciprocating engine converts the linear motion of a piston into rotational motion, while a gas turbine engine converts the thermal energy of a gas into rotational motion using a turbine.
What is the difference between a DC motor and an AC motor?
A DC motor runs on direct current, while an AC motor runs on alternating current. AC motors are typically simpler and more reliable than DC motors, but DC motors have better speed control and torque characteristics.