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Solving the labor saving principle of moving pulley
As shown in the figure on the left, the reason why the moving pulley saves effort is that the force of the same rope must be equal everywhere. If you look at the figure on the left, you can see that the moving pulley divides a rope into two ropes. The forces of the two ropes are equal, and they all pull objects upward. Therefore, the force you use is only half of the original force, and the other half of the force is from the wall
Using the principle of lever to explain the function of fixed pulley and movable pulley
Depressed. It's not in the book
Fixed pulley you take the center of the circle as the fulcrum to make the arm of force respectively. The arm of force is equal and the moment is equal, so you can't save effort
Moving pulley you take the side as the fulcrum, one arm of force is twice of the other
How to explain the labor saving phenomenon of moving pulley with lever principle?
The fixed pulley does not save effort. The movable pulley saves effort. It takes the fixed rope and the tangent point of the pulley as the axis. The gravity acts on the center of the circle, the arm of force R, and the tensile force acts on all other points. The maximum arm of force is 2R. According to the principle of lever, the movable pulley has a long arm of power and less power, which saves effort
Draw the fixed pulley and movable pulley and their lever diagram respectively
As shown in the picture
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