simple machines
easier－easy的比较级
They do this by reducing how much push or pull is needed to do work. 它们通过减少工作时需要的推力或拉力来达到这个（使工作更简单）。
simple 简单
parts 零件
lever
lever 杠杆
bottle opener 开瓶器
a hammer
hammer 锤子
nails 钉子
an inclined plane
inclined plane 斜面
ramp 斜坡
an inclined plane
force 力量
lift 抬
straight up 直直向上
distance 距离
a wedge
a screw
a pulley
pulleys
combine 合在一起
reduce 减少
a wheel and axle
a doorknob and a steering wheel
a compound machine
the can opener
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