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
ahemeral days
arbitrary-function generator
beam intensity distribution
beginning of conversation
calorie small
can you feel my world
carboxylic acrylonitrile butadiene rubber latex
cargo winch
champenize
chlorvinyldichloroarsine
chrome-manganese-silicon alloy steel
chromospheric eruption
cioteronel
coaminopherase
compilation order
computer main frequency
corporate group
corsse
cross-section ionization detector
cube farm
decade band
decentralised
deep trades
deformable raft
denounc't
diphthongise
do what one is capable of
dynamic geomorphology
electronic specific heat
emiss
feather picker
financial supervision
fire resistant paint
genus pezizas
get a patent on
get robbed
go with
Gran Colombia
grenade throwers
gyro-TWT
hanson
harebin
have one's bread buttered for life
highly-academic
insulinization
interference inversion
It's a small world.
large rock mass
lethrinus variegatus
linguistic description
lowest normal low water
Malvastrum coromandelianum
mangan-Rockbridgeite
manzanar
medium-intensity approach light system
mendigo
metranemia
Moorhusen
nag screens
oceanite
patholinguistics
patripassianism
persuing
phenanthrine
photopolymerization system
phototroller
project into
proofreadings
public decision making
pulse-power breakdown
pump power input
pyruric
Rami nasales anteriores laterales
range of mountains
rated revolutions
rheticus
risic acid
Réclère
self-blinded
separated layer fertilization
sexual chemistry
shrieved
shrinking and thinning
siphonuli
smallness of cornea
sokoloff
Spinoolivary
star cross
stowing machine
subclavial
tabp
temperature anomaly
tethery
time working day
time-life
transmitter frequency tolerance
u-verse
usuals
walking bosses
water discipline
wow us
Zhanay