(2014?Pingdingshan Model) The mechanical efficiency of a pulley block is shown in the figure. (1) Draw the most energy-saving way of winding the pulley block on the diagram. (2)

(1) when the pulley block is the most energy-saving, there should be 3 strands of rope acting on the movable pulley, the winding method is shown in the figure below:

(3) in order to measure the mechanical efficiency of the pulley block to lift the object, so it is necessary to read in the slow and uniform speed lifting, classmate B is correct;

(4) from the table can be seen, the total work W total = F rope rope s rope = 0.6N x 0.6m = 0.36J, the pulley block At this time mechanical efficiency η =

W useful

W total

×100%=

0.3J

0.36J

× 100% ≈ 83.3%;

(5) For the same pulley, if the weight of the lifted object increases, the mechanical efficiency will increase.

The answers are: (1) the pulley block is the most energy-saving winding as shown in the figure above; (3) B; in order to measure the mechanical efficiency of the pulley block to lift the object, it should be read at a slow and constant speed;

(4) 0.36; 83.3%; (5) <.