The Scientific definition of mass

What is the definition of mass in Science ?

The Scientific definition of mass   

The kilogram is defined in terms of a platinum–iridium standard mass kept near Paris. For measurements on an atomic scale, the atomic mass unit, defined in terms of the atom carbon-12, is usually used.

The international 1 kg standard of
mass, a platinum–iridium cylinder 3.9 cm in
height and in diameter.

The SI standard of mass is a cylinder of platinum and iridium  that is kept at the International Bureau of Weights and Measures near Paris and assigned, by

international agreement, a mass of 1 kilogram. Accurate copies have been sent to standardizing laboratories in other countries, and the masses of other bodies can be determined by balancing them against a copy. 

The U.S. copy of the standard kilogram is housed in a vault at NIST. It is removed, no more than once a year, for the purpose of checking duplicate copies that are used elsewhere. Since 1889, it has been taken to France twice for re-comparison with the primary standard.

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The Scientific Definition of Time or Second

What is the  Definition of Time Second in science ?

Scientific Definition of Time (Second)

Time defined to be 

"One second is the time taken by 9 192 631 770 oscillations of the light (of a specified

wavelength) emitted by a cesium-133 atom."

Time has two aspects. For civil and some scientific purposes, we want to know the time of day so that we can order events in sequence. In much scientific work, we want to know how long an event lasts. Thus, any time standard must be able to answer two questions: “When did it happen?” and “What is its duration?”

Any phenomenon that repeats itself is a possible time standard. Earth’s rotation, which determines the length of the day, has been used in this way for centuries. A quartz clock, in which a quartz ring is made to vibrate continuously, can be calibrated against Earth’s rotation via astronomical observations and used to measure time intervals in the laboratory. However, the calibration cannot be carried out with the accuracy called for by modern scientific and engineering technology.

ref :Fundamentals of Physics

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The Actual Scientific Definition of Length l

What is the correct  Definition of length in science ?

Scientific Definition of Length

meter defined to be 

"The meter is the length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second."

After a lot of modification this  set to be actual Scientific Definition of Length.

Background of the length 

In 1792, the newborn Republic of France established a new system of weights and measures. Its cornerstone was the meter, defined to be one ten-millionth of the distance from the north pole to the equator. 

Later, for practical reasons, this Earth standard was abandoned and the meter came to be defined as the distance between two fine lines engraved near the ends of a platinum–iridium bar, the standard meter bar, which was kept at the International Bureau of Weights and Measures near Paris. 

Accurate copies of the bar were sent to standardizing laboratories throughout the world. These secondary standards were used to produce other, still more accessible standards, so that ultimately every measuring device derived its authority from the standard meter bar through a complicated chain

of comparisons. 

Eventually, a standard more precise than the distance between two fine scratches on a metal bar was required. In 1960, a new standard for the meter, based on the wavelength of light, was adopted. Specifically, the standard for the meter was redefined to be 1 650 763.73 wavelengths of a particular orange-red light emitted by atoms of krypton-86 (a particular isotope, or type, of krypton) in a gas discharge tube that can be set up anywhere in the world. This awkward number of wavelengths was chosen so that the new standard would be close to the old meter-bar standard.

By 1983, however, the demand for higher precision had reached such a point that even the krypton-86 standard could not meet it, and in that year a bold step was taken.The meter was redefined as the distance traveled by light in a specified time interval. In the words of the 17th General Conference on Weights and Measures:

The meter is the length of the path traveled by light in a vacuum during a time

interval of 1/299 792 458 of a second.

Measurements of the speed of light had become extremely precise, so it made sense to adopt the speed of light as a defined quantity and to use it to redefine the meter.

Ref :Fundamentals of Physics

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What is the Defination and difference Position and Displacement

Difference between distance and displacement in physics and Definition

 Define Position 

The position x of a particle on an x axis locates the particle with respect to the origin, or zero point, of the axis.The position is either positive or negative, according to which side of the origin the particle is on, or zero if the particle is at the origin.The positive

direction on an axis is the direction of increasing positive numbers; the opposite direction is the negative direction on the axis.

"To locate an object means to find its position relative to some reference point, often the origin (or zero point) of an axis such as the x axis .The positive direction of the axis is in the direction of increasing numbers (coordinates), which is to the right.The opposite is the negative direction."

Define  displacement

"A change from position x1 to position x2 is called a displacement "

The displacement _x of a particle is the change in its position: x = x2 - x1.

Displacement is a vector quantity. It is positive if the particle has moved in the positive direction of the x axis and negative if the particle has moved in the negative direction.

Ref :Fundamental of Physics

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What is the properties of motion (kinematics)

Properties of Motion (Kinematics)

we shall examine some general properties of motion that is restricted in three ways.

1. The motion is along a straight line only.The line may be vertical, horizontal, or slanted, but it must be straight.
2. Forces (pushes and pulls) cause motion . In this chapter we discuss only the motion itself and changes in the motion. Does the moving object speed up, slow down, stop, or reverse direction? If the motion does change, how is time involved in the change?
3. The moving object is either a particle (by which we mean a point-like object such as an electron) or an object that moves like a particle (such that every portion moves in the same direction and at the same rate). A stiff pig slipping down a straight playground slide might be considered to be moving like a particle; however, a tumbling tumbleweed would not.

Ref : Fundamentals of Physics

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Definition of The International System of Units SI

What Is The International System of Units (SI)?

Definition of The International System of Units 

In 1971 the 14th General Conference on Weights and Measures picked seven quantities as base quantities, thereby forming the basis of the International System of Units, abbreviated SI from its French name and popularly known as the metric system.

The units for the three base quantities—length, mass, and time.

These units were  defined to be on a “human scale.” 

Units for Three SI  Base Quantities 

• Name         Unit         Symbol 

1. Length       meter        m 
2. Time          second       s 
3. Mass          kilogram    kg

Many SI derived units are defined in terms of these base units.

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