题目内容
From the passage we can learn that ______.
查看答案
搜索结果不匹配？点我反馈
更多问题
Which of the following statements is TRUE？
The problem of deciding at what point a baby's imitations can be considered as speech ______.
Is nothing sacred？ Even the idle weekend pastime of skimming stones on a lake has been taken apart and reduced to a mathematical formula.
Everyone knows a stone bounces best on water if it's round and flat, and spun towards the water as fast as possible. Some enthusiasts even travel to international stone-skimming competitions, like world champion Jerdone Coleman-McGhee, who made a stone bounce 38 times on Blanco River, Texas, in 1992.
Intuitively,a flat stone works best because a relatively large part of its surface strikes the water, so there's more bounce. Inspired by his eight-year-old son, physicist Lyderic Bocquet of Lyon University in France wanted to find out more. So he tinkered with some simple equations describing a stone bouncing on water in terms of its radius(半径) ,speed and spin, and taking account of gravity and the water's drag.
The equations showed that the faster a spinning stone is travelling, the more times it will bounce. So no surprise there. To bounce at least once without sinking, Bocquet found the stone needs to be travelling at a minimum speed of about 1 kilometre per hour.
And the equations also backed his hunch(直觉) that spin is important because it keeps the stone fairly flat from one bounce to the next. The spin has a gyroscopic(陀螺的) effect, preventing the stone from tipping and falling sideways into the water.
To match the world record of 38 bounces using a 10-centimetre-wide stone, Bocquet predicts it would have to be travelling at about 40 kilometres per hour and spinning at 14 revolutions a second. He adds that drilling lots of small pits in the stone would probably help, by reducing water drag in the same way that dim pies on a golf ball reduce air drag. "Although I suppose that would be cheating," says Bocquet.
He and his team at Lyon hope to design a motorized "catapult" that can throw stones onto a lake with a precise speed and spin, to test if the predictions stand up.
Bocquet adds that he's probably just rediscovering a piece of history. British engineer Barnes Wallis must have done the same sort of maths and experiments when he was designing his famous bouncing bombs for the Dambusters squadron(中队) during the Second World War.
Which of the following could be the best title for this passage？
Any attempt to trace the development from the noises babies make to their first spoken words leads to considerable difficulties. It is agreed that they enjoy making noises, and that during the first few months one or two noises sort themselves out as particularly indicative of delight, distress, sociability, and so on. But since these cannot be said to show the baby's intention to communicate, they can hardly be regarded as early forms of language. It is agreed, too, that from about three months they play with sounds for enjoyment, and that by six months they are able to add new sounds to their store. This self-imitation leads on to deliberate imitation of sounds made or words spoken to them by other people. The problem then arisen so to the point at which one can say that these imitations can be considered as speech.
It is a problem we need not get our teeth into. The meaning of a word depends on what a particular person means by it in a particular ,situation and it is clear that what a child means by a word will change as he gains more experience of the world. Thus the use,at say seven months, of "mama" as a greeting for his mother cannot be dismissed as a meaningless sound simply because he also uses it at other times for his father, his dog, or anything else he likes.
Playful and apparently meaningless imitation of what other people say continues after the child has begun to speak for himself. I doubt, however; whether anything is gained when parents cash in on this ability in an attempt to teach new sounds. (370w)
Children who start speaking late ______.
微信支付 
支付宝支付