an object that moves around an external axis is said to be
revolution or orbital revolution orbit
title: Rotation text: Rotation A rotation is a circular movement of an object around a center (or point) of rotation. A three-dimensional object can always be rotated around an infinite number of imaginary lines called "rotation axes" ( ). If the axis passes through the body's center of mass, the body is said to rotate upon itself, or spin. A rotation about an external point, e.g. the Earth about the Sun, is called a revolution or orbital revolution, typically when it is produced by gravity. The axis is called a pole. Mathematically, a rotation is a rigid body movement which, unlike a translation, title: Projectile motion text: Projectile motion Projectile motion is a form of motion experienced by an object or particle (a projectile) that is thrown near the Earth's surface and moves along a curved path under the action of gravity only (in particular, the effects of air resistance are assumed to be negligible). This curved path was shown by Galileo to be a parabola. The study of such motions is called ballistics, and such a trajectory is a "ballistic trajectory". The only force of significance that acts on the object is gravity, which acts downward, thus imparting to the object a downward acceleration. Because of title: Induced movement text: Induced movement Induced movement or induced motion is an illusion of visual perception in which a stationary or a moving object appears to move or to move differently because of other moving objects nearby in the visual field. It is interpreted in terms of the change in the location of an object due to the movement in the space around it. The object affected by the illusion is called the "target", and the other moving objects are called the "background" or the "context" (Duncker, 1929). A stationary object appears to move in the opposite direction to the background. For example, title: Circular motion text: Circular motion In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with constant angular rate of rotation and constant speed, or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves circular motion of its parts. The equations of motion describe the movement of the center of mass of a body. Examples of circular motion include: an artificial satellite orbiting the Earth at a constant height, a ceiling fan's blades rotating around a hub, a title: Coriolis force text: to the Northern Hemisphere. As the Earth turns around its axis, everything attached to it, including the atmosphere, turns with it (imperceptibly to our senses). An object that is moving without being dragged along with the surface rotation or atmosphere such as an object in ballistic flight or an independent air mass within the atmosphere, travels in a straight motion over the turning Earth. From our rotating perspective on the planet, the direction of motion of an object in ballistic flight changes as it moves, bending in the opposite direction to our actual motion. When viewed from a stationary point