2. Describe several related terms of lever.
Fulcrum: the point around which the lever (crowbar) rotates, marked with the letter O.
Power: draw a schematic diagram of the output by the force that makes the lever rotate, and use the letter F 1 or F.
Resistance: The force that prevents the lever from rotating is a schematic diagram of the output, marked with the letter F2 or F resistance. Note: Force and resistance make the lever rotate in the opposite direction, but their directions are not necessarily opposite.
Arm of force: the distance from the fulcrum to the line of force action. It is marked with the letter L 1 or L.
Resistance arm: the distance from the fulcrum to the line of resistance action, marked with the letter L2 or L resistance.
3. Drawing of the force arm: first determine the fulcrum of the lever, and then determine the line of action of the force. Then draw a vertical line from the fulcrum to the line of action of the force with a right triangle. The vertical foot should fall under the action of force. The symbol indicates which line segment is the arm of force, and the letter L 1 or l is written. The arm of force is usually drawn with a dotted line.
4. Study the equilibrium condition of lever.
(1) Lever balance means that the lever is stationary or rotating at a constant speed.
(2) Experimental purpose: To study the equilibrium condition of lever.
(3) Only when the lever is balanced in the horizontal position, the distance from the fulcrum to the action line of power (resistance) force, that is, the length of the arm of force, can be directly read from the scale value on the lever.
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