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In the International System of Units (SI), the unit of measurement of momentum is the kilogram metre per second (kg⋅m/s), which is dimensionally equivalent to the newton-second. Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it.
The first table lists the fundamental quantities used in the International System of Units to define the physical dimension of physical quantities for dimensional analysis. The second table lists the derived physical quantities. Derived quantities can be expressed in terms of the base quantities.
Units for other physical quantities are derived from this set as needed. In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form = where is the acceleration in ft/s 2 and g c = 32.174 lb·ft/(lbf·s 2).
Meaning SI unit of measure alpha: alpha particle: angular acceleration: radian per second squared (rad/s 2) fine-structure constant: unitless beta: velocity in terms of the speed of light c: unitless beta particle: gamma: Lorentz factor: unitless photon: gamma ray: shear strain: radian
The definition of angular momentum for a single point particle is: = where p is the particle's linear momentum and r is the position vector from the origin. The time-derivative of this is: The time-derivative of this is:
The SI units are defined by declaring that seven defining constants [1]: 125–129 have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to establish the value and associated uncertainty of a quantity of the same kind as the ...
The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380 649 × 10 −23 J⋅K −1, (J = kg⋅m 2 ⋅s −2), given the definition of the kilogram, the metre, and the second. K: SI: Physics: Basic: mole: mol: N: amount of substance: The amount of substance of exactly 6.022 140 76 × 10 23 elementary entities.
The first group of metric units are those that are at present defined as units within the International System of Units (SI). In its most restrictive interpretation, this is what may be meant when the term metric unit is used. The unit one (1) is the unit of a quantity of dimension one. It is the neutral element of any system of units. [2]