Newton's law of motion in Physics In a rough horizontal plane, there are two pieces of wood 1 and 2 with mass M1 and M2 respectively. In the middle, a light spring with original length L and stiffness coefficient K is used to connect them. The sliding friction coefficient between the wood block and the ground is u. now a horizontal force F is used to pull the wood block 2 to the right. When the two pieces of wood accelerate, what is the elastic force on the spring?

Newton's law of motion in Physics In a rough horizontal plane, there are two pieces of wood 1 and 2 with mass M1 and M2 respectively. In the middle, a light spring with original length L and stiffness coefficient K is used to connect them. The sliding friction coefficient between the wood block and the ground is u. now a horizontal force F is used to pull the wood block 2 to the right. When the two pieces of wood accelerate, what is the elastic force on the spring?

Let the elastic force be F1 and the acceleration be a
For 2, f-f1 - μ m2g = M2A
For 1, there is F1 - μ m1g = m1a
Solvable F1 = m1f / (M1 + m2)

On the integral method in high school physics mechanics
1. Application conditions (the concept of system)
2. Principle (why can it be used in this way)
If one is at constant speed and the other is at rest, then the acceleration is not the same

I haven't touched high school textbooks for a long time, Khan
In fact, the holistic method is not difficult. In force analysis, multiple objects are regarded as a whole, and the effect between each part can be ignored. It can be regarded as internal force. Just like a person, it is generally regarded as an object, but there are forces between human bones, muscles, and organs, but these forces belong to the interior of the human body, which can offset each other and have no effect on the overall movement mode
The principle is that the forces are equal in magnitude and opposite in direction

When an object is on an inclined plane and decomposed orthogonally along the inclined plane, does the resultant force on the line of the vertical inclined plane necessarily equal to 0?

When an object is on an inclined plane and decomposed orthogonally along the inclined plane, the line resultant force of the vertical inclined plane must be equal to zero (under the condition that the inclined plane does not move)