Since 2012, the AU is defined as 1.495 978 707 ×10 11 m exactly, and the equation can no longer be taken as holding precisely. Definition Īccording to Newton's law of universal gravitation, the magnitude of the attractive force ( F) between two point-like bodies is directly proportional to the product of their masses, m 1 and m 2, and inversely proportional to the square of the distance, r, directed along the line connecting their centers of mass: The first implicit measurement with an accuracy within about 1% is attributed to Henry Cavendish in a 1798 experiment. The modern notation of Newton's law involving G was introduced in the 1890s by C. In SI units, its value is approximately 6.674 ×10 −11 m 3⋅kg −1⋅s −2. The measured value of the constant is known with some certainty to four significant digits. In the Einstein field equations, it quantifies the relation between the geometry of spacetime and the energy–momentum tensor (also referred to as the stress–energy tensor). In Newton's law, it is the proportionality constant connecting the gravitational force between two bodies with the product of their masses and the inverse square of their distance. The gravitational constant (also known as the universal gravitational constant, the Newtonian constant of gravitation, or the Cavendish gravitational constant), denoted by the capital letter G, is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's theory of general relativity. The value of g n as used in the official definition of the kilogram-force is used here for all gravitational units.The gravitational constant G is a key quantity in Newton's law of universal gravitation. using a slightly conservative and easier to calculate value) is a good rule of thumb. On the Earth's surface, 1 kN is about 101.97162 kilogram-force of load, but multiplying the kilonewton value by 100 (i.e. Injection molding machines, used to manufacture plastic parts, are classed by kilonewton (i.e., the amount of clamping force they apply to the mold). The safe working loads in both tension and shear measurements can be stated in kilonewtons. They are also often used in the specifications for rock climbing equipment. Kilonewtons are often used for stating safety holding values of fasteners, anchors, and more in the building industry. It is common to see forces expressed in kilonewtons or kN, where 1 kN = 1,000 N.Ĭommon use of kilonewtons in construction.m = 1 J ( joule), the SI unit of energy.The Work-Energy Theorem states that the work done on a body is equal to the change in energy of the body. Thus, in SI units, a force of 1 N exerted over a distance of 1 m is 1 N The dot product of force and distance is mechanical work.The force of Earth's gravity on (= the weight of) a human being with a mass of 70 kg is approximately 686 N.The approximation of 1 kgf corresponding to 10 N (1 decanewton or daN) is sometimes used as a rule of thumb in everyday life and in engineering. On Earth's surface, a mass of 1 kg exerts a force of approximately 9.8 N (or 1.0 kilogram-force 1 kgf = 9.80665 N by definition).1 N is the force of Earth's gravity on a mass of about 100 g = ( 1∕ 9.81 kg).The newton is the SI unit for force it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second squared. 3 Common use of kilonewtons in construction.
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