FEA interview questions in Engineering mechanics

1.Define: Moment of a force

• Moment of force is the Product of magnitude of force and distance between line of action of force, point about which the force causing rotation.

2.What is moment of inertia?

• Moment again multiplied by distance between line of action of force point about which the force causing rotation.     
• The moment of inertia which forms the basis of dynamics of rigid bodies and strength of materials.

3.What is area moment of inertia? What is it significance and its conjunction?

• Moment of inertia for plane figures is called area moment of inertia.
• When examined by itself there is no physical important for moment of inertia. It’s a just mathematical expression usually denoted by I.
• Structural meaning of Moment of inertia Measure ability of the beam to resist bending.
• Area moment inertia is conjunction with deflection or deformation.

4.What is mass moment of inertia? And it’s the structural meaning?

• Moment of inertia for Solid or 3D figures is called mass moment of inertia.it is conjunction with rotation of rigid bodies.
• Structural meaning of mass moment of inertia Measure of resistance of a body to rotation.

5.What is Polar moment of inertia? And it’s the structural meaning?

• Polar moment of inertia is equal to the sum of area moments of inertia about any two mutually perpendicular axes in its plane and intersecting on the polar axis.
• Structural meaning of Polar Moment of inertia Measure ability of the Shaft to resist torsion

6.What is Radius of gyration or radius of rotation?

Distance from that axes at which all the elemental parts of the lamina would have to be placed

                   

  r =√ I/A

       Where,

                   r – Radius of gyration

                   I – Moment of inertia

                   A – Area

7.What is centroid?

• The point where the whole area of the figure is assumed to be concentrated.
• It is also called as Centre of area.
• Which is same as Centre of gravity when the bodies have area only and not weight.
• The weightless lamina’s, plane figures have Centroid.

8.What is centre of gravity?

• The point through the whole weight of the body assumed to act.
• The position of the c.g depends upon the shape of the body. C.g may be within the boundary of the body or outside of the boundary of the body.

9.How to determine centre of gravity of object?

  There are two methods to find the centre of gravity.

1. Balancing method
2. Suspension method

FEA interview questions in Engineering mechanics

1. What is force?

• A force can affect both the motion and the deformation of the body on which it acts. Forces may arise from direct contact between bodies, or they may be applied at a distance (such as gravitational attraction).
• Contact forces are distributed over a surface area of the body, whereas forces acting at a distance are distributed over the volume of the body.

2. Classification of force?

3. What are Characteristics of a force?

There are two Characteristics of force.

Magnitude

Direction

This makes force as a vector quantity. Having both magnitude and direction.

4. What is meant by Resultant Force?

N number of the forces acting in a system, can be replaced by a single force, Which could produce the same effect as produced by the all the forces, that single force is called resultant force.

5. State Lami's theorem?

• If three coplanar, concurrent and non-collinear forces acting on a particle keep it in equilibrium, each is proportional to the sine of the angle between the other two.
• According to the theorem, where A, B and C are the magnitudes of three coplanar, concurrent and non-collinear forces, which keep the object in static equilibrium, and α, β , γ are the angles directly opposite to the forces A, B and C respectively.
A/sinα =B/ sin β = c/ sin γ

6. Triangle law of forces?

Triangle law of forces states that, If two forces acting at a point are represented in magnitude and direction by the two adjacent sides of a triangle taken in order, then the closing side of the triangle represents the resultant of the force.

7. Polygon law of forces?

If a number of forces acting at a point be represented in magnitude and direction by the sides of a polygon in order, then the resultant of all these forces may be represented in magnitude and direction by the closing side of the polygon taken in opposite order.

8. What is the procedure to draw the free-body diagram?

• Isolation of a part from the system
• Show all the forces acting on the part
1. Active forces – tends to set the particle in motion.
2. Reactive forces – Results of constraints or supports that tend to prevent motion.
• Identify each forces
1. The forces that are unknown must labeled with their proper magnitude and directions.

FEA Interview Questions in Engineering Mechanics:

1. What is mechanics and its classifications?

• Mechanics is a branch of the physical science that is concerned with the state of rest or motion of bodies that are subjected to the action of forces.
• In general, this mechanics can be classified as below:

2. What is rigid body?

A rigid body can be considered as a combination of a large number of particles in which all the particles remain at a fixed distance from one another, both before and after applying a load.(No deformation)

In most cases the actual deformations occurring in structures, machines, mechanisms, and the like are relatively small, and the rigid-body assumption is suitable for analysis.

3. State: Newton’s Three Laws of Motion.

First law:
• If a particle is at rest (or moving with constant velocity in a straight line), it will remain at rest (or continue to move with constant velocity in a straight line) unless acted upon by a force.

Second law:

• A particle acted upon by a force will accelerate in the direction of the force. The magnitude of the acceleration (a) is proportional to the magnitude of the force(F) and inversely proportional to the mass (m) of the particle.

F=ma Where F - Applied force M - Mass of the particle A- Acceleration of the particle

Third Law:

• For every action, there is an equal and opposite reaction; that is, the forces of interaction between two particles are equal in magnitude and oppositely directed along the same line of action.

4. What is equilibrium of a particle or system?

• A particle is said to be in equilibrium if it remains at rest if originally at rest, or has a constant velocity if originally in motion
• Static equilibrium” is used to describe an object at rest.
• To maintain equilibrium, it is necessary to satisfy Newton’s first law of motion, which requires the resultant force acting on a particle to be equal to zero.
• This condition may be stated mathematically as
  
  ∑F = 0
  

5. What is the difference between scalar and Vector?

A scalar is a quantity that has magnitude only.	A vector is a quantity that possesses magnitude and direction and obeys the parallelogram law.
E.x. Length, Mass, Pressure	E.x. Weight, Force

6. What is free body diagram?

• A free body diagram is a graphical illustration of an isolated section or member of a part or a system.
• Used visualize the applied forces and moments and resulting, reactions, on a body in steady state condition (not in accelerated condition).
• Free body diagram must satisfy the equations of static equilibrium in the principles of statics.

7. What is moment?

• When a forces are applied to the body, it rotate about a Center point which is not in the line of action of force is called moment.
• This tendency is called “torque”.

Moment=force Χ distance which is perpendicular the direction of force

M= Fd

Where, M- Moment F- Force d- Distance which is perpendicular the direction of force

8. What is couple?

• Two parallel, noncollinear forces that are equal in magnitude act in opposite direction is called couple .
• Its effect is to produce pure rotation or tendency for a rotation in a specified direction.
• Resultant force value of a couple is zero.

9. What is Friction?

When two surfaces are in contact with each other one surface tend to move with respect to the other, tangential force will be developed at the contact surface in the opposite direction of motion is called friction.

10. Friction is advantage or disadvantage? Justify?

Friction force has both advantage and disadvantage.

Advantage:

• Friction between floor and feet, Enable us to walk on floor(less friction makes us to slide)
• Friction between road and Vehicle, help us to ride vehicles on road.
• Transmission of power using belt…and the like.

Disadvantage:

• Wear between components in a system
• Tear
• Loss of power, Loss of energy…etc.