“mass”的概念、定义、翻译、参考文献-科学参考

mass

Physics

A measure of a body’s inertia, i.e. its resistance to acceleration. According to Newton’s laws of motion, if two unequal masses, m₁ and m₂, are allowed to collide, in the absence of any other forces both will experience the same force of collision. If the two bodies acquire accelerations a₁ and a₂ as a result of the collision, then m₁a₁=m₂a₂. This equation enables two masses to be compared. If one of the masses is regarded as a standard of mass, the mass of all other masses can be measured in terms of this standard. The body used for this purpose is a 1-kg cylinder of platinum–iridium alloy, called the international standard of mass. Mass defined in this way is called the inertial mass of the body.

Mass can also be defined in terms of the gravitational force it produces. Thus, according to Newton’s law of gravitation, m_g=Fd²/MG, where M is the mass of a standard body situated a distance d from the body of mass m_g; F is the gravitational force between them and G is the gravitational constant. The mass defined in this way is the gravitational mass. In the 19th century Lóránd Eötvös (1848–1919) showed experimentally that gravitational and inertial mass are indistinguishable, i.e. m_i=m_g. Experiments performed in the 20th century have confirmed this conclusion to even greater accuracy.

Although mass is formally defined in terms of its inertia, it is usually measured by gravitation. The weight (W) of a body is the force by which a body is gravitationally attracted to the earth corrected for the effect of rotation and equals the product of the mass of the body and the acceleration of free fall (g), i.e. W=mg. In the general language, weight and mass are often used synonymously; however, for scientific purposes they are different. Mass is measured in kilograms; weight, being a force, is measured in newtons. Weight, moreover, depends on where it is measured, because the value of g varies at different localities on the earth’s surface. Mass, on the other hand, is constant wherever it is measured, subject to the special theory of relativity. According to this theory, announced by Albert Einstein in 1905, the mass of a body is a measure of its total energy content. Thus, if the energy of a body increases, for example by an increase in kinetic energy or temperature, then its mass will increase. According to this law an increase in energy Δ‎E is accompanied by an increase in mass Δ‎m, according to the mass–energy equation Δ‎m=Δ‎E/c², where c is the speed of light. Thus, if 1 kg of water is raised in temperature by 100 K, its internal energy will increase by 4 × 10⁻¹² kg. This is, of course, a negligible increase and the mass–energy equation is only significant for extremely high energies. For example, the mass of an electron is increased sevenfold if it moves relative to the observer at 99% of the speed of light.

The origin of mass is not yet fully understood.

Mathematics

With any body there are associated two parameters: the gravitational mass, which occurs in the inverse square law of gravitation, and the inertial mass, which occurs in Newton’s second law of motion. While they are distinct in definition, no experiment has shown a difference between gravitational and inertial mass.

The SI unit of mass is the kilogram. See also rest mass. Compare weight.

Astronomy

A measure of the amount of matter in a body. Mass gives rise to the inertia of an object, i.e. its resistance to change in its motion or state of rest; this is known as the inertial mass. It also produces a gravitational force (see Gravitation). Although mass is formally defined in terms of its inertia, it is usually measured by the effects of its gravitation. The equivalence principle of general relativity asserts that inertial mass and gravitational mass are equal for all bodies, and experiments have verified this equality to one part in 10¹². The weight of a body is the force by which it is gravitationally attracted to the Earth. Although the terms ‘mass’ and ‘weight’ are often used interchangeably on Earth, in space a body may be weightless but still retain its inertia, i.e. it still requires a force to change its motion. According to the special theory of relativity, the mass of a body increases as its velocity approaches that of light. At the speed of light itself the mass would be infinite.

Space Exploration

The quantity of matter in a body as measured by its inertia, including all the particles of which the body is made up. Mass determines the acceleration produced in a body by a given force acting on it, the acceleration being inversely proportional to the mass of the body. The mass also determines the force exerted on a body by gravity on Earth, although this attraction varies slightly from place to place (the mass itself will remain the same). In the SI system, the base unit of mass is the kilogram.
At a given place, equal masses experience equal gravitational forces, which are known as the weights of the bodies. Masses may, therefore, be compared by comparing the weights of bodies at the same place. The standard unit of mass to which all other masses are compared is a platinum-iridium cylinder of 1 kg, which is kept at the International Bureau of Weights and Measures in Sèvres, France.

Chemistry

A measure of a body’s inertia, i.e. its resistance to acceleration. According to Newton’s laws of motion, if two unequal masses, m₁ and m₂, are allowed to collide, in the absence of any other forces both will experience the same force of collision. If the two bodies acquire accelerations a₁ and a₂ as a result of the collision, then m₁a₁ = m₂a₂. This equation enables two masses to be compared. If one of the masses is regarded as a standard of mass, the mass of all other masses can be measured in terms of this standard. The body used for this purpose is a 1-kg cylinder of platinum-iridium alloy, called the international standard of mass.

Chemical Engineering

A measure of the quantity of material. It is defined as the resistance or inertia of a body to acceleration. Newton’s laws of motion state that if two bodies of equal mass, m, each acquire an acceleration, a, then $m_{1} a_{1} = m_{2} a_{2}$ . That is, the mass of one body can be compared to the other. A standard mass is therefore used to compare all other masses. This is a one-kilogram cylinder of platinum-iridium alloy called the international standard of mass.

单词	mass
释义	mass Physics A measure of a body’s inertia, i.e. its resistance to acceleration. According to Newton’s laws of motion, if two unequal masses, m₁ and m₂, are allowed to collide, in the absence of any other forces both will experience the same force of collision. If the two bodies acquire accelerations a₁ and a₂ as a result of the collision, then m₁a₁=m₂a₂. This equation enables two masses to be compared. If one of the masses is regarded as a standard of mass, the mass of all other masses can be measured in terms of this standard. The body used for this purpose is a 1-kg cylinder of platinum–iridium alloy, called the international standard of mass. Mass defined in this way is called the inertial mass of the body. Mass can also be defined in terms of the gravitational force it produces. Thus, according to Newton’s law of gravitation, m_g=Fd²/MG, where M is the mass of a standard body situated a distance d from the body of mass m_g; F is the gravitational force between them and G is the gravitational constant. The mass defined in this way is the gravitational mass. In the 19th century Lóránd Eötvös (1848–1919) showed experimentally that gravitational and inertial mass are indistinguishable, i.e. m_i=m_g. Experiments performed in the 20th century have confirmed this conclusion to even greater accuracy. Although mass is formally defined in terms of its inertia, it is usually measured by gravitation. The weight (W) of a body is the force by which a body is gravitationally attracted to the earth corrected for the effect of rotation and equals the product of the mass of the body and the acceleration of free fall (g), i.e. W=mg. In the general language, weight and mass are often used synonymously; however, for scientific purposes they are different. Mass is measured in kilograms; weight, being a force, is measured in newtons. Weight, moreover, depends on where it is measured, because the value of g varies at different localities on the earth’s surface. Mass, on the other hand, is constant wherever it is measured, subject to the special theory of relativity. According to this theory, announced by Albert Einstein in 1905, the mass of a body is a measure of its total energy content. Thus, if the energy of a body increases, for example by an increase in kinetic energy or temperature, then its mass will increase. According to this law an increase in energy Δ‎E is accompanied by an increase in mass Δ‎m, according to the mass–energy equation Δ‎m=Δ‎E/c², where c is the speed of light. Thus, if 1 kg of water is raised in temperature by 100 K, its internal energy will increase by 4 × 10⁻¹² kg. This is, of course, a negligible increase and the mass–energy equation is only significant for extremely high energies. For example, the mass of an electron is increased sevenfold if it moves relative to the observer at 99% of the speed of light. The origin of mass is not yet fully understood. Mathematics With any body there are associated two parameters: the gravitational mass, which occurs in the inverse square law of gravitation, and the inertial mass, which occurs in Newton’s second law of motion. While they are distinct in definition, no experiment has shown a difference between gravitational and inertial mass. The SI unit of mass is the kilogram. See also rest mass. Compare weight. Astronomy A measure of the amount of matter in a body. Mass gives rise to the inertia of an object, i.e. its resistance to change in its motion or state of rest; this is known as the inertial mass. It also produces a gravitational force (see Gravitation). Although mass is formally defined in terms of its inertia, it is usually measured by the effects of its gravitation. The equivalence principle of general relativity asserts that inertial mass and gravitational mass are equal for all bodies, and experiments have verified this equality to one part in 10¹². The weight of a body is the force by which it is gravitationally attracted to the Earth. Although the terms ‘mass’ and ‘weight’ are often used interchangeably on Earth, in space a body may be weightless but still retain its inertia, i.e. it still requires a force to change its motion. According to the special theory of relativity, the mass of a body increases as its velocity approaches that of light. At the speed of light itself the mass would be infinite. Space Exploration The quantity of matter in a body as measured by its inertia, including all the particles of which the body is made up. Mass determines the acceleration produced in a body by a given force acting on it, the acceleration being inversely proportional to the mass of the body. The mass also determines the force exerted on a body by gravity on Earth, although this attraction varies slightly from place to place (the mass itself will remain the same). In the SI system, the base unit of mass is the kilogram. At a given place, equal masses experience equal gravitational forces, which are known as the weights of the bodies. Masses may, therefore, be compared by comparing the weights of bodies at the same place. The standard unit of mass to which all other masses are compared is a platinum-iridium cylinder of 1 kg, which is kept at the International Bureau of Weights and Measures in Sèvres, France. Chemistry A measure of a body’s inertia, i.e. its resistance to acceleration. According to Newton’s laws of motion, if two unequal masses, m₁ and m₂, are allowed to collide, in the absence of any other forces both will experience the same force of collision. If the two bodies acquire accelerations a₁ and a₂ as a result of the collision, then m₁a₁ = m₂a₂. This equation enables two masses to be compared. If one of the masses is regarded as a standard of mass, the mass of all other masses can be measured in terms of this standard. The body used for this purpose is a 1-kg cylinder of platinum-iridium alloy, called the international standard of mass. Chemical Engineering A measure of the quantity of material. It is defined as the resistance or inertia of a body to acceleration. Newton’s laws of motion state that if two bodies of equal mass, m, each acquire an acceleration, a, then $m_{1} a_{1} = m_{2} a_{2}$ . That is, the mass of one body can be compared to the other. A standard mass is therefore used to compare all other masses. This is a one-kilogram cylinder of platinum-iridium alloy called the international standard of mass.
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