Applied Mechanics interview questions

Applied Mechanics is a branch of physical science that deals with the practical application of mechanics. It involves the study of forces, motions, and the resulting deformations and stresses in solid and fluid bodies. It is foundational to many engineering disciplines, particularly civil and mechanical engineering.

• Statics: The study of bodies at rest or in equilibrium, where the sum of forces and moments acting on the body is zero.
• Dynamics: The study of bodies in motion, which includes kinematics (describing motion) and kinetics (analyzing the forces causing motion).

A free-body diagram is a graphical representation used to show all external forces and moments acting on a body. It is an essential tool in mechanics for solving problems related to equilibrium, motion, and deformation.

• First Law (Law of Inertia): A body at rest will remain at rest, and a body in motion will continue in uniform motion unless acted upon by a net external force.
• Second Law (Law of Acceleration): The acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma).
• Third Law (Action and Reaction): For every action, there is an equal and opposite reaction.

The principle of superposition states that the total response (deformation, stress, strain) in a linear elastic system subjected to multiple loads is equal to the sum of the responses caused by each load acting individually. This principle is valid only for linear systems.

A body is in equilibrium when the sum of all forces and the sum of all moments acting on it are zero. For a body to be in static equilibrium:

• The sum of forces in all directions must be zero: ∑F = 0.
• The sum of moments about any point must be zero: ∑M = 0.

• Stress: The internal resistance offered by a material to an external force, defined as force per unit area (σ = F/A).
• Strain: The deformation or displacement in a material caused by stress, expressed as the change in length per unit length (ε = ΔL/L).

Hooke's Law states that, within the elastic limit of a material, the stress applied to it is directly proportional to the resulting strain. Mathematically, it is expressed as σ = Eε, where E is the modulus of elasticity (Young's modulus).

• Fixed Support: Restrains all translational and rotational movements.
• Pinned Support: Allows rotation but restrains translation in any direction.
• Roller Support: Allows translation in one direction and rotation but restrains translation in the perpendicular direction.

The moment of inertia is a measure of an object's resistance to rotational motion about an axis. It depends on the distribution of mass relative to the axis of rotation. It is crucial in engineering for analyzing and designing beams, shafts, and other structural elements subjected to bending and torsion.