As the picture shows, Xiao Ming wants to carry a bag of grain from the ground to the roof. Without considering the weight and friction of the rope, Xiao Ming lifted a bag of 40 N grain with a moving p

As the picture shows, Xiao Ming wants to carry a bag of grain from the ground to the roof. Without considering the weight and friction of the rope, Xiao Ming lifted a bag of 40 N grain with a moving pulley. Xiao Ming works hard w = GH = 40n×10m = 400J;

Total work w' = fs = 25n×20m = 500j；;

So the mechanical efficiency: η = 400J500J×100% = 80%;

If a bag of grain weighing 100N is lifted to the same height at a uniform speed, the mechanical efficiency of this moving pulley will increase, because the extra work remains unchanged, but the useful work will increase.

So, the answer to this question is: 400,500,80%, getting bigger.