# Table of Quantities and Units

The following tables list some common physical, mechanical, and electrical quantities, along with their units and the corresponding symbols.

• In cases where a quantity has two or more commonly used units (such as force, which can have units of either newtons or pounds), these units and their symbols are listed on separate lines.
• Note that the same symbol may be used for more than one quantity, in which case the context will make clear which quantity is intended. For example, T can be used to represent either period or tension.

General Physical Quantities: These quantities are widely used in physics, mechanical engineering, electrical engineering, and other fields.

 Quantity Symbol Unit Symbol for the Unit acceleration a meters per second per second m/s2 angle θ or φ radian rad degree ° angular frequency ω radians per second rad/sec energy W joule J force F newton N pound lb mass m kilogram kg period T second s power P watt W time t second s velocity v meters per second m/s miles per hour mph

Mechanical Quantities: These quantities are used in statics, dynamics, strength of materials, and other areas studied by mechanical engineers.

 Quantity Symbol Unit Symbol for the Unit bending moment M pound inch lb·in newton meter N·m distributed load q pounds per inch lb/in newtons per meter N/m elastic modulus (also called Young’s modulus) E pounds per square inch lb/in2 newtons per square meter N/m2 flexural rigidity EI pound inches squared lb·in2 newton meters squared N·m2 normal stress σ pounds per square inch lb/in2 newtons per square meter N/m2 second moment of area I inches to the fourth in4 meters to the fourth m4 shear force V pound lb newton N shear stress τ pounds per square inch lb/in2 newtons per square meter N/m2 spring rate k newtons per meter N/m tension T newton N pound lb weight W newton N pound lb

Electrical Quantities: These quantities are used in circuit analysis and other areas studied by electrical engineers.

 Quantity Symbol Unit Symbol for the Unit capacitance C farad F charge Q coulomb C current I ampere A impedance Z ohm Ω inductance L henry H reactance X ohm Ω resistance R ohm Ω voltage V volt V