Hello, the main knowledge of the answer is 1. Newton's first law: when there is no external force, all objects always remain stationary or move in a straight line at a constant speed. Newton's first law is further deduced on the basis of empirical facts, so it can't be proved by experiments.

2. Inertia: The property that an object keeps its state of motion unchanged is called inertia. Newton's first law is also called the law of inertia.

3. The state of balance of an object: When an object is acted by several forces, we say that these forces are in a state of balance if it stays still or moves in a straight line at a constant speed. When an object is in equilibrium under the action of two forces, it is called two-force equilibrium.

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Constant.

4. Conditions for the balance of two forces: If the two forces acting on the same object are equal in magnitude and opposite in direction, the resultant force when the two forces are balanced on the same straight line is zero.

5. An object will remain stationary or move in a straight line at a constant speed without force or balance force.

Chapter 11 Simple induction of mechanical and power knowledge

1. lever: a hard rod that can rotate around a fixed point under the action of force is called a lever.

2. What are fulcrum, strength, resistance, force arm and resistance arm?

(1) fulcrum: the point (o) around which the lever rotates.

(2) Force: the force that makes the lever rotate (F 1)

(3) Resistance: the force that prevents the lever from rotating (F2)

(4) Arm of force: the distance from the fulcrum to the line of force action (L 1).

(5) Resistance arm: the distance from the fulcrum to the line of resistance action (L2)

3. Conditions of lever balance: power × power arm = resistance × resistance arm. Or written as: F 1L 1=F2L2 or written as. This equilibrium condition is also the lever principle discovered by Archimedes.

I hope I can help you.