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If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B, each body is subject to an attractive force F g = Gm A m B /r 2, where G = 6.67 × 10 −11 N⋅kg −2 ⋅m 2 is the "universal gravitational constant". This is sometimes referred to as gravitational mass.
L. Use of the Terms "Mass" and "Weight" [See Section K. NOTE] When used in this handbook, the term "weight" means "mass". The term "weight" appears when inch-pound units are cited, or when both inch-pound and SI units are included in a requirement. The terms "mass" or "masses" are used when only SI units are cited in a requirement.
electron mass: 9.109 383 7139 (28) ... While the values of the physical constants are independent of the system of units in use, each uncertainty as stated reflects ...
The poundal is defined as the force necessary to accelerate an object of one-pound mass at 1 ft/s 2, and is equivalent to about 1/32.2 of a pound-force. The slug is defined as the amount of mass that accelerates at 1 ft/s 2 when one pound-force is exerted on it, and is equivalent to about 32.2 pounds (mass).
Mass refers to the intrinsic property of all material objects to resist changes in their momentum. Weight, on the other hand, refers to the downward force produced when a mass is in a gravitational field. In free fall, (no net gravitational forces) objects lack weight but retain their mass. The Imperial units of mass include the ounce, pound ...
In other words, most of what composes the "mass" of ordinary matter is due to the binding energy of quarks within protons and neutrons. [26] For example, the sum of the mass of the three quarks in a nucleon is approximately 12.5 MeV/c 2, which is low compared to the mass of a nucleon (approximately 938 MeV/c 2).
The concept of mass conservation is widely used in many fields such as chemistry, mechanics, and fluid dynamics. Historically, mass conservation in chemical reactions was primarily demonstrated in the 17th century [2] and finally confirmed by Antoine Lavoisier in the late 18th century.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.