时间:2019-02-24 作者:英语课 分类:英语听力文摘 English Digest


英语课

  Remember seesaws 2? Those things were great. But there was often a problem.

Suppose there’s a big kid on one side and a smaller kid on the other side. The seesaw 1 just stays in one position: big kid on the ground, smaller kid up in the air. No fun. After a few different tries, you probably realized that moving the big kid in toward the center made it possible to rock a little. Move the big kid even more and you can achieve balance. Now the seesaw works.

What’s going on here? The answer is in the “center of mass.” The center of mass is a point somewhere along the plank 3 that holds the two kids where their average weight falls. If you can get the center of mass to be over the pivot 4 point, the seesaw will be balanced.

There’s a simple way to figure out where the center of mass is. If the big kid is two times as heavy as the little kid, then their mutual 5 center of mass will be two times closer to the big kid than to the little kid. Three times heavier and the center of mass will be three times closer. And so on.

So the reason the heavy kid sits on the ground while the light kid is up in the air is that their mutual center of mass is on the heavy kid’s side of the pivot. To make the seesaw work, the heavy kid must push that center of mass forward until it just touches the pivot. Then their average weight pushes right on the middle, letting the ends rock up and down.



n.跷跷板
  • Prices have gone up and down like a seesaw this year.今年的价格像跷跷板一样时涨时跌。
  • The children are playing at seesaw.孩子们在玩跷跷板。
n.跷跷板,上下动( seesaw的名词复数 )v.使上下(来回)摇动( seesaw的第三人称单数 );玩跷跷板,上下(来回)摇动
n.板条,木板,政策要点,政纲条目
  • The plank was set against the wall.木板靠着墙壁。
  • They intend to win the next election on the plank of developing trade.他们想以发展贸易的纲领来赢得下次选举。
v.在枢轴上转动;装枢轴,枢轴;adj.枢轴的
  • She is the central pivot of creation and represents the feminine aspect in all things.她是创造的中心枢轴,表现出万物的女性面貌。
  • If a spring is present,the hand wheel will pivot on the spring.如果有弹簧,手轮的枢轴会装在弹簧上。
adj.相互的,彼此的;共同的,共有的
  • We must pull together for mutual interest.我们必须为相互的利益而通力合作。
  • Mutual interests tied us together.相互的利害关系把我们联系在一起。
学英语单词
Adelphan-Esidrex
ahaptoglobinemia
Alfarelos
alice walkers
antiferromagnetically-coupled media
Ban Klang Dong
black-greiest
blue beeches
cellular-phone
colour inheritance
commuter train
composite shipbuilder
coral reefs
costocoracoid
curvilinear style
cyanalcohol
Daarlerveen
disposingly
Disse's spaces
drainage-tube
ectotrophic symbiosis
el carmen (carmen)
erasble optical disk
excitoreflex
fairgoers
familial histiocytic reticulosis
farrowing fever
follow my nose
for certainty
Full Packaged Product
gelicolous
graphic voltmeter
health insurance unit
high-viscosity pump
hitting people
huelga
importance(of a flare)
indexed sequential data set
indisciplined
inella verrucosa
keeper current
Kjeldahl analysis
klopemania
leprose
lobuli corticales (renis)
Millridge
Moroline
moulting liquid
mountainview
multiengined airplane
multiple-tariff meter
Mycobacterium friedmannii
myeloarchitectural
myiasis muscosa
mylar film
Neanderthaloid
obstructive glaucoma
odium
over-pot
pannor
pappuses
paraproteinaemia
pasan
pauselessly
phyllostomids
piesmatids
pocket accumulator
pressure distillation
price convention
programming theory
Raja batis
rubber bowl
Salching
sallusts
Sandy Plains
sessilinasis
ship shock
Snihurivka
soum
spiric
split-second collet tube
Staurograptus
string parsing
swap, pin
synonym ring
tape preamplifier
tetrasymmetric face
the lie of the land
Truro
two-sheave block
Ulmipollenites
ultralite
underdry
Urausu
vasopressinergic
vegetable drug
verification of forecast
Vincent's infection of tonsil
von Gierke
walk point
wave traps
Yongpyong-dong