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1. Scientific knowledge.

a) Tools and machinery.

1 Machinery refers to various devices composed of mechanical principles. Levers, pulleys, bevels, axles, etc., are all machinery. Simple machines are also commonly referred to as tools.

2 There are three points of leverage: force point, fulcrum point, and resistance point. When the distance from the force point to the fulcrum is greater than the distance from the resistance point to the fulcrum, the lever is labor-saving; When the distance from the force point to the fulcrum is equal to the distance from the resistance point to the fulcrum, the lever is effortless and effortless; When the distance from the point of force to the fulcrum is less than the distance from the point of resistance to the fulcrum, the lever is laborious.

Whether a lever is labor-saving or not is determined by the position of its three points.

The three points of the leverage can be separated, and whether it is labor-saving) can be judged

3 The axle is composed of a wheel and an axle, the force on the wheel can save effort, the larger the wheel, the more labor, the axle is a special lever.

4. The fixed pulley is fixed in one place and cannot move with the movement of heavy objects, such as the pulley on the top of the flagpole; The movable pulley is not fixed and can move with the movement of heavy objects. The fixed pulley is effortless and effortless, but the direction of the force can be changed, and it can be seen as an equal-arm lever; The movable pulley cannot change the direction of the force, but it can save the force, f=1 2

g。The pulley block can both change the direction of the force and save the force exponentially. The more groups of pulleys (1 fixed pulley and 1 movable pulley are combined into 1 group), the more labor-saving it is, which is related to the number of rope strands wound around the movable pulley. i.e. f=1 n

A simple machine like a wooden plank attached to the car compartment.