书城教材教辅科学读本(英文原版)(套装1-6册)
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第83章 第一册(83)

"He squeezed a sponge up in his hand. It sprang back when he opened his hand, because it is elastic. "He forced a cork into a bottle. The cork went in, because he made it smaller by squeezing it. When he pulled the cork out again, it sprang back to itsright shape and size, because it is elastic.

"So you see, Norah, all these things-the india- rubber, flannel, cloth, cane, whalebone, sponge, and cork-are elastic, but they are not elastic in quite the same way. One shows that it is elastic when it is pulled, another when it is bent, and another when it is squeezed out of shape."SUMMARY

India-rubber stretches when we pull it, and springs back when we let go. It is elastic, and so are cloth and flannel. Whale-bone and cane bend easily, but spring back when we let go. They are elastic.

Sponge and cork can be squeezed, and made smaller, but they spring back when we let go. Sponge and cork are elastic.