(2010? Liaocheng) Use the experimental device as shown in the figure to measure the mechanical efficiency of the lever. During the experiment, pull the spring dynamometer vertically upward at a const

(2010? Liaocheng) Use the experimental device as shown in the figure to measure the mechanical efficiency of the lever. During the experiment, pull the spring dynamometer vertically upward at a constant speed so that it hangs on a relatively small

As can be seen from the figure, the graduation value of the spring dynamometer is 0.1N, so its indication is 0.5N.

During the experiment, the useful work is: W useful=Gh=1N×0.1m=0.1J

The total work is: W total=Fs=0.5N×0.3m= 0.15J

So the mechanical efficiency of the lever is: η = W useful W total = 0.1J0.15J = 66.7%

So the answer is: 0.5; ?66.7; the lever has its own weight.