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inertia
inertia , in physics, the resistance of a body to any alteration in its state of motion , i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of motion. Inertia is a property common to all matter. This property was first...
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motion
motion the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; velocity is a vector quantity, having both magnitude and direction, while speed is a scalar qu...
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Newton's laws of motion
Newton's laws of motion Three laws published in 1687 by I.Newton concerning the motion of bodies:1.A body continues in a state of uniform rest or motion unless acted upon by an external force.2.The acceleration produced when a force acts is directly proportional to the force and takes place in the ...
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perpetual-motion machine
perpetual-motion machine device that would be able to operate continuously and supply useful work, in violation of the laws of thermodynamics . A machine that would produce more energy in the form of work than is supplied to it in the form of heat would violate the first law of thermodynamic...
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celestial mechanics
celestial mechanics the study of the motions of astronomical bodies as they move under the influence of their mutual gravitation . Celestial mechanics analyzes the orbital motions of planets, dwarf planets, comets, asteroids, and natural and artificial satellites within the solar system as well as...
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Copernican system
Copernican system first modern European theory of planetary motion that was heliocentric, i.e., that placed the sun motionless at the center of the solar system with all the planets, including the earth, revolving around it. Copernicus developed his theory in the early 16th cent. from a study of ...
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centripetal force and centrifugal force
centripetal force and centrifugal force action-reaction force pair associated with circular motion . According to Newton's first law of motion, a moving body travels along a straight path with constant speed (i.e., has constant velocity ) unless it is acted on by an outside force . For circular ...
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proper motion
proper motion in astronomy, apparent movement of a star on the celestial sphere , usually measured as seconds of arc per year; it is due both to the actual relative motions of the sun and the star through space. Proper motion reflects only transverse motion, i.e., the component of motion across th...
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Lenz's law
Lenz's law physical law, discovered by the German scientist H. F. E. Lenz in 1834, that states that the electromotive force (emf) induced in a conductor moving perpendicular to a magnetic field tends to oppose that motion. When an electric motor is in operation, the armature is turning in a mag...
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momentum
momentum , in mechanics, the quantity of motion of a body, specifically the product of the mass of the body and its velocity . Momentum is a vector quantity; i.e., it has both a magnitude and a direction, the direction being the same as that of the velocity vector. When an external force acts upon ...
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