Basics of Mechanical Engineering - Part 01

BASICS OF MECHANICAL ENGINEERING

1.      Define Force?

Force is an action that causes a free object with nonzero, finite mass to accelerate, relative to a non-accelerating frame of reference. Force is the effect that produces the phenomenon of weight for objects with nonzero, finite mass.

Unit of force is Newton (N). 1 N =  1 kgm/s ²
Eg: Force include the thrust of a rocket engine. 

2.      Define Inertia Force?
         An imaginary force supposed to act upon an accelerated body, equal in magnitude and opposite in direction to the resultant of the real forces.

3.      Define Moment of Inertia?

           The tendency of a body to resist angular acceleration, expressed as the sum of products of the 

       each particle in the body and square of its perpendicular distance from the axis of rotation.

I = mk² (kg m²)

            Where, I  - Moment of Inertia
                        m - Mass of an object/body (kg)
                        k  -  Radius of Gyration (m)

4.      Define Torque?

It is defined as the product of the force and the perpendicular distance of its line of action from the given axis of point.

It is also defined as the tendency of a force that rotate an object about an axis or a point

Torque (T) = Force (F) x Radius (r).

Unit of torque id Newton meter (Nm).

5.      Define Newton’s Viscous Law?

Newton’s viscous law states that the magnitude of shear stress is directly proportional to the velocity gradient (dv/dy).

τ α (dv/dy)

6.      What is mean by ductile failure?

Ductile failure happens in the following stages.
1. Yield as first stage of failure,
2. Some hardening at second stage,
3. Breaking/Failure after a possible necking formation.

7.      Define Factor of Safety (FOS)?

The ratio of the maximum stress that a structural part or other piece of material can withstand to the maximum stress estimated for it in the use for which it is designed.

It is also known as Safety Factor.

Factor of Safety (FOS) = Maximum Stress / Working Stress.
Where,
      Maximum Stress = Yield Stress (Ductile Material) & Ultimate Stress (Brittle Material)

8.      Define Stress?
The force of resistance per unit area offered by a body against deformation is known as stress.
Stress = Load / Area
Unit-N/m²

9.      Define Strain?

The ratio of change in dimension by original dimension is known as strain. Strain is dimensionless.