小雨用滑轮组提升重物.每个滑轮等重,不计绳重、摩擦和水的阻力.请画出与解题过程相应的受力分析示意图.
关于杠杆,下列说法中正确的是( )
—How do you go to school, Mr. Li?
—I _____________ to school, because it is good for my health.
下图涉及的两个机构的共同特点是( )