挖掘机的手臂为什么能挖起几吨重的土?它的胳膊肘怎么这么有劲?
How does an excavator lift tons of dirt with one arm?
挖掘机手臂的每个关节都藏着液压油缸:机器把油用高压压进缸里,推动像手臂骨头一样的钢杆,小小的泵就能产生大象腿般的推力。液压系统还能把力量精确分配到铲斗、大臂和小臂,所以它能又轻又准地把树苗种好,也能掀翻巨石。
Every joint hides a hydraulic cylinder: the machine pushes oil in at high pressure, driving steel rods like arm bones — a small pump makes elephant-strength pushes. Hydraulics split power precisely among bucket, arm and boom, so it plants seedlings gently yet flips boulders.
难度 进阶 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《十万个为什么》第六版建筑与交通分册,少年儿童出版社,2013
Ten Thousand Whys: Architecture and Transportation volume, 6th ed., Juvenile and Children Publishing House, 2013
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-7-5324-9328-9 · 核验依据 2 ISBN 9787532493289
#液压系统 #挖掘机 #杠杆力量
飞机那么重,翅膀又不动,它凭什么飞上天?
Heavy planes with fixed wings — what keeps them flying?
机翼产生升力靠两件事配合:翼型上弯下平让上方气流更快、压强更低(伯努利原理);同时机翼带迎角把下方空气向下推,获得反作用升力(牛顿第三定律)。两者共同贡献升力,缺一不可。起飞前机场还要算好速度、重量与天气——升力必须超过重力才能离地。
Wings make lift two ways together: curved upper surfaces speed airflow lowering pressure above (Bernoulli), while angle of attack shoves air downward earning reaction lift (Newton's third law). Both matter. Before takeoff crews compute speed, weight and weather — lift must beat gravity to leave ground.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《十万个为什么》第六版航空与航天分册,少年儿童出版社,2013
Ten Thousand Whys: Aviation and Aerospace volume, 6th ed., Juvenile and Children Publishing House, 2013
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-7-5324-9328-9 · 核验依据 2 ISBN 9787532493289
#升力 #伯努利原理 #迎角
电梯是怎么把我们送上高楼的?它会累吗?
How do elevators carry us up tall buildings? Do they get tired?
电梯像一个会飞的房间,头顶有结实的钢缆拉着它,机器轮子慢慢收放缆绳,它就稳稳上下。电梯不会累,但很守纪律:超重了会响铃,门没关好就不出发。
An elevator is a flying room held by strong steel cables. Machines wind them slowly and it glides up and down. Elevators never tire, but they follow rules: too heavy rings a bell, doors must close before moving.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
David Macaulay,《The Way Things Work》,Houghton Mifflin,1988
David Macaulay, The Way Things Work, Houghton Mifflin, 1988
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL15130328W：The Way Things Work（按标
#电梯 #钢缆 #安全