Constant force work

The power of changing force

Instantaneous power

average power

Note here that when solving the problem of the momentum theorem before, we integrated over time. The internal forces were vector summed and then integrated. The total effect was zero.

The sum of the work of forces and the sum of the work of forces are not the same thing

Characteristics of a pair of internal strength skills

Conservative and non-conservative forces

Object system potential energy

Review: We discussed momentum before. The momentum in the center of mass system is zero.

Now: Discuss kinetic energy. There is kinetic energy in the center of mass system and there is also kinetic energy in the static system.

The work done by the external force is zero

Communicated between mechanics and other disciplines

Energy rich

Previous: Solving for post-collision velocity, simultaneous conservation of momentum and conservation of mechanical energy (with squares, tedious calculations)

Now: simultaneous conservation of momentum and collision law (restitution coefficient equals 1)

The recovery coefficient e is only related to the material

The law of collision can be extended to oblique collision, and it holds true for any normal direction of the point of action of two objects.

Each velocity in the collision law is expressed by coordinates perpendicular to the surface direction, that is, the velocity of each point has positive and negative