The pulley block is used to pull the object a on the horizontal ground to move forward at a uniform speed of 5m within 10s. If the weight of the object is 10000n, the friction between the object and the ground is 200N, the mechanical efficiency of the pulley block is 80%, and the friction of the machine itself is not taken into account. To find out (1) how much work is done by the pulling force? How much extra work is done? (2) how much is the pulling force F? (3) how much is the pulling force power?

Wyou = 200N * 5m = 1000j, wtotal = 1000j / 0.8 = 1250j, 1250j is the total work, which is the work of pulling force, w = 1250j-1000j = 250j
F pull = 1250j / 5m * 2 (force on two sections of rope) = 125N, P pull = 1250j / 10s = 125w

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