- Definition:- force acts on free moving object which cause to acclerate or deccelerat. If the force acts on stationary object it can deform or eve break. According to Newton's Second Law: F= m X a . whereas ;
- F: force in newton (N)
- m: mass in kilogram (kg)
- a: acceleration (m/s²)
Pressure:-
- Definition: Is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.
Whereas :-- P: pressure in Pascal (Pa)
- F: force in Newton (N)
- A: area in m²
Stress:-
- Definition: force acts upon an object which can not be moved.
where , 
- Stress: N/m².
- Force: N
- Area: m²
Strain:-
- Definition: It is relative longitudinal change in body length.
There is no unit for strain.
- L: original lenght.
- ∆L: change in lenght.
The strain can be positive (tensile) or negitive (compressive).
Stress Vs. Strain:-
Hook's law describes the relation between the stress and strain as follows:
where,
- σ: stress in N/m².
- E: modulus of electricity of object in N/m².
- ε: strain.
Measurment of force and pressure:-
Force: The simplest type of measuring devices is the spring balance. The scale is calibrated in Newton and/or gram.
Pressure: Mechanical measuring devices were designed where Bourdon tubes or bellows are used to produce a mechanical displacement that is transferrd to an indicating pointer.
