Question

如圖所示是小型建筑工地上使用的“罐籠式”提升機，用它能將放在罐籠A中的建筑材料提升到高處。已知被提升的建筑材料的質(zhì)量為280kg，拉力F將它以0.5m/s的速度勻速提升到10m的高度，拉力F的功率為2kW。不計摩擦及鋼絲繩、動滑輪的重。求：

（1）拉力F對所提升的建筑材料做的功是多少？

（2）罐籠A的重力是多少？

（3）提升機在提升建筑材料時的機械效率是多少？

 

Answer 1

（1）G_材=m_材g=280kg×10N/kg=2.8×10³N···························································· （1分）

           W=G_材h=2800N×10m=2.8×10⁴J························································ （1分）

（2）P=Fv

繩

F===2×10³N····························································· （1分）

G_A=2F－G_材=2×2×10³N－2.8×10³N =1.2×10³N···························· （1分）

      （3）W_總=FS=2×10³N×20m=4×10⁴J ··················································· （1分）

W總

          η=70%·································································· （1分）