题型:问答题 简答题 Ann doesn’t like milk.She said that she never ___it at home.A.use to drinkingB.used to drinkingC.used to drinkD.use to drink 查看答案
题型:问答题 简答题 如图所示,建筑工地上的吊车是靠电动机来提升货物,货物重 1800N,电动机正常工作时钢绳的拉力为750N,20s内将货物匀速提升了6m。(忽略各种摩擦)求:(1)电动机卷绳子的速度(2)动滑轮的重(3)滑轮的机械效率 查看答案