3. How do you know where the wind is blowing from? 4. Do you think air and wind are important to you? Why? Write 30 words or more. 相关知识点: 试题来源: 解析 1. 当风吹的时候,我们能感受到脸上的风。 2. 我们需要空气来呼吸和生存。 3. 通过观察风向标,我们可以知道风从哪里吹来。 4....
A. We float in the air. B. We push the ground backwards with our feet and the ground pushes us forward. C. The ground moves away from us. D. We don't interact with the ground. 相关知识点: 试题来源: 解析 B。解析:当我们走路时,我们用脚向后推地面,地面会以大小相等的力向前推我们...
2. How does a balloon float in the sky? 3. Can we live without the air? 4. What can we do to protect the air? Write 30 words or more. 相关知识点: 试题来源: 解析 1. We can feel the air all the time, but we notice it most when the wind blows. 2. A balloon floats be...
Buoyancy is the ability to float in water or other fluids. Sharks need to put effort into remaining buoyant. In fact, if they stop swimming they will sink. Most bony fish have a swim bladder. A swim bladder is an internal organ filled with gas that helps the fish float without having t...
In addition to using the bathroom regularly, astronauts need to do all of the same things they do on Earth, including eating and sleeping. Of course in space, the lack of gravity makes everyday activities not so ordinary. With no refrigerator on-board the spacecraft to keep food fresh (al...
They do so by letting precise amounts of water or air into their ballast tanks. Photo courtesy of US Navy.Buoyancy on the surfaceNow most boats don't operate in quite the same way as submarines. They don't sink, but they don't exactly float either. A boat partly floats and partly ...
Hot air balloons do this with a burner positioned under an open balloon envelope. As the air in the balloon cools, the pilot can reheat it by firing the burner. Modern hot air balloons heat the air by burning propane, the same substance commonly used in outdoor cooking grills. The ...
One of the things I love about flying these helium balloons is they have the capability for real expedition level flights.我喜欢飞这些氦气球的原因之一是它们是真正的探险级别的飞行。What I'm talking about is flights of 23,000 feet in an open gondola carried only by helium balloons.我说的是...
30.Balloonsfloatintheair___boatsdoonthesea.A.justasB.whenC.thatD.where 31.--Ifyouareofferedatriptothemoon,___it?--Ofcourse.Whynot? A.didyouaccept B.areyougoingtoaccept C.willyouaccept D.wouldyouaccept 32.Itisreportedthatmanyanewhouse___atpresentinthedisasterareaA.arebeingbuilt B.werebeing...
How Do Planes Fly: Thrust and Drag Airplanes take advantage of four forces. Lee Dempsey/HowStuffWorks.com Drop a stone into the ocean and it will sink into the deep. Chuck a stone off the side of a mountain and it will plummet as well. Sure, steel ships can float and even very ...