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The International Committee for Weights and Measures (CIPM) approved a revision in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.626 070 15 × 10 −34 kg⋅m 2 ⋅s −1, effectively defining the kilogram in terms of the second and the metre. The new definition took effect on 20 May 2019.
The metre–kilogram–second–coulomb (MKSC) and metre–kilogram–second–ampere (MKSA) systems are examples of such systems. [ 38 ] [ 21 ] The metre–tonne–second system of units (MTS) was based on the metre, tonne and second – the unit of force was the sthène and the unit of pressure was the pièze .
A newton is defined as 1 kg⋅m/s 2 (it is a named derived unit defined in terms of the SI base units). [1]: 137 One newton is, therefore, the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force.
There are gram calories and kilogram calories. One kilogram calorie, which equals one thousand gram calories, often appears capitalised and without a prefix (i.e. Cal) when referring to "dietary calories" in food. [17] It is common to apply metric prefixes to the gram calorie, but not to the kilogram calorie: thus, 1 kcal = 1000 cal = 1 Cal.
When an object's weight (its gravitational force) is expressed in "kilograms", this actually refers to the kilogram-force (kgf or kg-f), also known as the kilopond (kp), which is a non-SI unit of force. All objects on the Earth's surface are subject to a gravitational acceleration of approximately 9.8 m/s 2.
Only like terms may be added. When a unit is divided by itself, the division yields a unitless one. When two different units are multiplied or divided, the result is a new unit, referred to by the combination of the units. For instance, in SI, the unit of speed is metre per second (m/s). See dimensional analysis.
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vehicle-kilometre (vkm [1]) as a measure of traffic flow, determined by multiplying the number of vehicles on a given road or traffic network by the average length of their trips measured in kilometres. [2] vehicle-mile (vehicle miles traveled, or VMT [1]) same as before but measures the trip expressed in miles.