时间:2019-03-06 作者:英语课 分类:英语时差8,16


英语课

 Sit on a swing, let someone push you, and away you go.   But what happens if the person who pushed you walks away, and you want to swing faster and higher. If you've ever been in the second grade, you know the solution to that. Just start pumping your legs--stretching them forward then drawing them up underneath 1 you--and you can make yourself swing higher. Have you ever wondered why this is?


Swings work by converting 2 potential energy into kinetic 3 energy, then kinetic energy back into potential energy, over and over again. The kinetic energy is the fast part of swinging; it's the speed you have as you rush back and forth 4. Potential energy is the high part of swinging. The higher you go on the swing, the more potential energy you have. Even though you're not moving at the very top of each swing, you can think of your height as your potential for speed. A physicist 5 would say that your kinetic energy--that is, your speed--is "stored" as potential energy at the top of each swing. More height is more speed, just waiting to happen.
You can increase the energy of your swing in two separate ways. If someone pushes you, that increases your kinetic energy. By pumping your legs, you can increase your potential energy. By raising your legs at the top of each swing, you can raise the overall center of mass of your body, effectively raising the height of your swing.
Pump after pump, the energy you burn in your legs increases your swing's potential energy. That extra height will add up, giving you a wilder swing ride. 

adj.在...下面,在...底下;adv.在下面
  • Working underneath the car is always a messy job.在汽车底下工作是件脏活。
  • She wore a coat with a dress underneath.她穿着一件大衣,里面套着一条连衣裙。
n.吹(炉冶)炼,转炉炼钢v.(使)转变( convert的现在分词 );(使)转化;皈依;改变(信仰)
  • Jim's got some half-baked idea about converting his garage into a sauna. 吉姆初步计划把他的车库改造成一个蒸汽浴室。 来自《简明英汉词典》
  • Quite recently man has succeeded in converting sunlight directly into electrical energy. 最近人们已经成功地把太阳光直接转化为电能。 来自《现代汉英综合大词典》
adj.运动的;动力学的
  • There exist many sources of energy both potential and kinetic.存在着许多势能和动能的能源。
  • The kinetic theory of gases is the best known example.气体动力学理论就是最有名的例子。
adv.向前;向外,往外
  • The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
  • He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。
n.物理学家,研究物理学的人
  • He is a physicist of the first rank.他是一流的物理学家。
  • The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。
学英语单词
absolute cell reference
adapter skirt
Advanced Energy Projects
air traveller
ala dag
Alcyonium
antidrought
aortic obstruction
arc welding engine generator
audioboard
automatic traction equipment
back end-to
basin of attraction
benzimidazoyl
berthages
bohnckes
capacitance coupled
Carex stipata
Caughnawaga
cavity boundary
collied
combustion conditions
commissura posrerior grisea
consolidated statement of cost goods sold
cowherd
crank shaft timing gear
desorption column
dissuader
distributed group decision support system
dry basis moisture content
dry-silver print
dummy out
earthy
Epleys
equicharacteristic
european blackbirds
Expectations Theory
favourous
flight control computer (fcc)
full word integer overflow
fungisterol ergosterol
gear teeth vernier
genus cuterebras
Gomorraha
hardface
Heave aback!
Hoagland solution
hold something in derision
hovercam
injection-valve opening pressure
interbifid grooves
junior school
knife edge test
laocon
level checking
Logovoy
machine mixing
macroslope
menispermaceous
microaneurisms
microvacuolar
millikan method
mixed-up observations
more-detailed
national revolution
nonalinement
notchers
on a razor-edge
ouatite
parabolic cylinder function
Paraguayans
persuadedness
pinotages
planetary radiation budget
pollaplonyx opacipennis
polyvinylidene fluoride
pontious
Primula florindae
programmed temperature works
quality of labor
scotopic eye
sdat
self-dramatizings
sodium ruthenate
soliloquizer
stacking height
Streptothrix
sulcus terminalis
tagging
there's one born every minute
traffic link
Tragacete
ubiquinol
Ugli
undemonstratively
unguerdoned
unit service factor
vignetting diaphragm
whole body radiation
with a heavy tread
work from home
zircon concentrate