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Point mass (pointlike mass) is the concept, for example in classical physics, of a physical object (typically matter) that has nonzero mass, and yet explicitly and specifically is (or is being thought of or modeled as) infinitesimal (infinitely small) in its volume or linear dimensions.
The Bondi mass was introduced (Bondi, 1962) in a paper that studied the loss of mass of physical systems via gravitational radiation. The Bondi mass is also associated with a group of asymptotic symmetries, the BMS group at null infinity. Like the SPI group at spatial infinity, the BMS group at null infinity is infinite-dimensional, and it also ...
a point such that the translational motion is zero or simplified, e.g. on an axle or hinge, at the center of a ball and socket joint, etc. When the center of mass is used as reference point: The (linear) momentum is independent of the rotational motion. At any time it is equal to the total mass of the rigid body times the translational velocity.
The n-body problem considers n point masses m i, i = 1, 2, …, n in an inertial reference frame in three dimensional space ℝ 3 moving under the influence of mutual gravitational attraction. Each mass m i has a position vector q i. Newton's second law says that mass times acceleration m i d 2 q i / dt 2 is equal to the sum of the ...
The theorem tells us how different parts of the mass distribution affect the gravitational force measured at a point located a distance r 0 from the center of the mass distribution: [13] The portion of the mass that is located at radii r < r 0 causes the same force at the radius r 0 as if all of the mass enclosed within a sphere of radius r 0 ...
Similarly, for a point mass the moment of inertia is defined as, = where is the radius of the point mass from the center of rotation, and for any collection of particles as the sum, =. Angular momentum's dependence on position and shape is reflected in its units versus linear momentum: kg⋅m 2 /s or N⋅m⋅s for angular momentum versus kg⋅m ...
The curve () describes the deflection of the beam in the direction at some position (recall that the beam is modeled as a one-dimensional object). is a distributed load, in other words a force per unit length (analogous to pressure being a force per area); it may be a function of , , or other variables.
The delta function was introduced by physicist Paul Dirac, and has since been applied routinely in physics and engineering to model point masses and instantaneous impulses. It is called the delta function because it is a continuous analogue of the Kronecker delta function, which is usually defined on a discrete domain and takes values 0 and 1.