Dive into the Principles of Dynamics and MOND

Study Notes

The text discusses the concept of momentum.
Momentum is the product of an object's mass and velocity.
A point mass is a body with negligible dimensions relative to the reference system.
When a force is applied to a point mass, its momentum changes proportionally.
The change in momentum is determined by the force and the duration of the force application.
The law of conservation of momentum states that the total momentum of a closed system remains constant.
In a closed system, the momentum of one object can be transferred to another object.
Momentum is a vector quantity, meaning it has both magnitude and direction.
The unit of momentum is kilogram-meter per second (kg*m/s).
Momentum is an important concept in physics and has many practical applications.
The principles of dynamics apply to inertial systems
The second principle states that force is proportional to acceleration
The third principle requires that action and reaction are always opposite and instantaneous
To extend the principles to non-inertial systems, the concept of "action" is restricted to forces and moments
In mechanics, generalized forces are real and reciprocal, implying a reaction
The preferred term today is "interaction" to emphasize the symmetry of the concept
An inertial system is defined by the manifestation of only real interactions between bodies
Apparent interactions are those that are not reciprocal and are attributed to the system
The second principle is related to the concept of energy
The third principle implies a constraint between distant points outside their respective light cones.
Mordehai Milgrom proposed a modification to Newtonian dynamics in 1981.
The modification is called MOND (Modified Newtonian Dynamics).
MOND aims to explain the rotation curves of spiral galaxies without the need for dark matter.
The modification takes into account the "break" in the acceleration of objects at low gravitational fields.
MOND is not widely accepted in the scientific community.
It is considered falsifiable, like theories of dark matter and dark energy.
The principles of dynamics are not absolute and can be modified.
References to principles of dynamics are not unreal, but rather not absolute.
The modification proposed by Milgrom is an alternative to the introduction of dark matter.
The modification is controversial and has not gained widespread acceptance.