The recurring boy and girl watching a toy boat float while a small rock sinks in shallow water.

Big question

为什么船会浮在水上，可是石头会沉下去？

Wèishénme chuán huì fú zài shuǐ shàng, kěshì shítou huì chén xiàqù?

Why does a boat float but a rock sink?

船会浮起来，是因为它的形状能让水把它托住；石头通常会沉下去，是因为它又小又重，挤得很紧。

Chuán huì fú qǐlái, shì yīnwèi tā de xíngzhuàng néng ràng shuǐ bǎ tā tuōzhù; shítou tōngcháng huì chén xiàqù, shì yīnwèi tā yòu xiǎo yòu zhòng, jǐ de hěn jǐn.

水会往上托东西。船会把重量摊开，而且里面有很多空间，所以水比较能把它托起来。很多石头对自己的大小来说太重了，所以水没有办法像托船那样托住它们。

Shuǐ huì wǎng shàng tuō dōngxi. Chuán huì bǎ zhòngliàng tānkāi, érqiě lǐmiàn yǒu hěn duō kōngjiān, suǒyǐ shuǐ bǐjiào néng bǎ tā tuō qǐlái. Hěn duō shítou duì zìjǐ de dàxiǎo lái shuō tài zhòng le, suǒyǐ shuǐ méiyǒu bànfǎ xiàng tuō chuán nàyàng tuōzhù tāmen.

你还见过什么东西会浮起来？又见过什么东西会沉到底下呢？

Nǐ hái jiànguo shénme dōngxi huì fú qǐlái? Yòu jiànguo shénme dōngxi huì chén dào dǐxia ne?

A boat can float because its shape helps water hold it up, but a rock is packed too tightly and usually sinks.

Water pushes up on things. A boat spreads its weight out and has space inside, so the water can support it. Many rocks are heavy for their size, so the water cannot hold them up the same way.

What else have you seen float, and what have you seen sink to the bottom?