quality discontinuity

Continuous quality

The impulse of the net external force experienced by an object during motion is equal to the increment of the momentum of the object

average force

In a certain period of time, the vector sum of the impulses of all external forces acting on a particle at the same time is equal to the increment of the total momentum of the particle system.

If the vector sum of the external forces on the system is zero, the total momentum of the system remains unchanged.

Applicable conditions

Inertial frame same reference frame

The moment of the resultant force about the reference point 0

If the external force acting on the particle has a moment of zero at a given point, then the angular momentum of the particle with respect to point 0 remains unchanged during the motion (angular momentum is a constant vector)

The sum of the work done by all external forces and all internal forces on the system of particles is equal to the increment of the total kinetic energy of the system of particles

When the system changes from state 1 to state 2, the increment of its mechanical energy is equal to the sum of the work of the external force and the work of the non-conservative internal force.

If a system only has conservative internal forces that do work, and other internal forces and all external forces do not do work, then the kinetic energy and potential energy of each object in the system can be converted into each other, but the total mechanical energy remains unchanged.

The work done has nothing to do with the path, only the starting and ending positions.

It’s not just about the starting and ending locations, it’s also about the path

Relative displacement

The energy associated with the position of a particle in a conservative force field

The component of a conservative force along a coordinate axis is equal to the negative value of the derivative of the potential energy about this coordinate axis

The work done by the combined external force on the particle is equal to the increment of the kinetic energy of the particle

inertial frame

mechanical energy loss