Results 1–10 of 10 for Newton%E2%80%99s gravitational law
Every object in the universe attracts every other object with a force (gravitational force FG) directed along the line through centres of the two objects that is proportional to the product of their masses and inversely proportional to the square of the distance between them.
m1 and m2 are masses of the two objects and r is the distance between them. G is universal constant of gravitation, which equals 6.67•10-26 N m2 kg-2. Strictly speaking, this law applies only to objects that can be considered pointlike object. Otherwise, the force has to be found by integrating the forces between various mass elements.
It is more properly to express Newton’s gravitational law by vector equation:
in which r1 and r2 are position vectors of masses m1 and m2.
Gravitational forces act on distance. Newton’s gravitational law is derived from Kepler’s law for planetary motion, using a physical assumption considering Sun as the centre and the source of gravitational force.
Additionally, every object moves in the direction of the force acting on it, with acceleration that is inversely proportional to the mass of object. For bodies on the surface of Earth, the distance r in gravitational law formula is practically equal to the Earth radius, RE. If the mass of the body on Earth surface is m and the mass of earth is ME, the gravitational force acting on that body can be expressed as:
where g is gravitational acceleration which is, although dependent on geographical latitude, usually considered as constant equal to 9.81 m s-2.
Gravitational constant (G) is the universal constant in the equation for the gravitational force between two particles
where r is the distance between the particles and m1 and m2 are their masses.
Ampere (A) is the SI base unit of electric current.
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10-7 newton per metre of length.
Joule (J) is the SI derived unit of energy, work, and heat. The joule is the work done when the point of application of a force of one newton is displaced a distance of one metre in the direction of the force (J = N m). The unit was named after the British scientist James Prescott Joule (1818-1889).
Gilbert Newton Lewis (1875-1946) is an American chemist whose theory of the electron pair fostered understanding of the covalent bond and extended the concept of acids and bases.
Potential energy (Ep) is the energy stored in a body or system as a consequence of its position, shape, or state (this includes gravitation energy, electrical energy, nuclear energy, and chemical energy). Gravitational potential energy is the energy associated with the state of separation between bodies that attracts each other via gravitational force. Elastic potential energy is the energy associated with the state of compression or extension of an elastic object. Thermal energy is associated with the random motions of atoms and molecules in a body.
Specific weight (γ) is defined as the ratio between the weight of a mass element, Δm, and the volume, ΔV, occupied by that element. As density (average) is defined as the ratio of a mass element and its volume, specific weight is equal to:
where g is gravitational acceleration.
Heat always flows from a higher to a lower temperature level. The driving force for the heat flux lies in the temperature difference ΔT between two temperature levels. Analogous to Ohm’s law, the following holds:
where H = dQ/dt is heat flux, measured in watts, ΔT is temperature difference across the thermal resistance, measured in kelvin, and Rth is thermal resistance, measured in K/W.
For example, suppose there were two houses with walls of equal thickness; one is made of glass and the other of asbestos. On a cold day, heat would pass through the glass house much faster. The thermal restistance of asbestos is then higher than of glass.
If the thermal Ohm’s law is divided by the heat capacity C, Newton’s law of cooling is obtained:
where dT/dt is rate of cooling or heating, measured in K s-1, and C is heat capacity, measured in J K-1.
Generalic, Eni. "Newton%E2%80%99s gravitational law." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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