Does a tennis ball bounce entirely because of the air inside?

网球(wǎng qiú)落地(luò dì)后(hòu)会(huì)弹(tán)起来(qǐ lái)，这(zhè)全(quán)靠(kào)球(qiú)里面(lǐ miàn)的(de)气(qì)吗(ma)？

A tennis ball bounces after hitting the ground; does that depend entirely on the air inside it?

有些(yǒu xiē)网球(wǎng qiú)里面(lǐ miàn)的(de)气压(qì yā)和(hé)外面(wài miàn)差不多(chà bù duō)，却(què)也(yě)能(néng)弹(tán)起来(qǐ lái)。

Some tennis balls have almost the same air pressure inside as outside, yet they still bounce.

原来(yuán lái)，里面(lǐ miàn)的(de)气(qì)不是(bù shì)唯一(wéi yī)的(de)原因(yuán yīn)。

The air inside is therefore not the only reason.

加压(jiā yā)网球(wǎng qiú)里面(lǐ miàn)的(de)气压(qì yā)比(bǐ)外面(wài miàn)高(gāo)，球(qiú)的(de)弹性(tán xìng)较多(jiào duō)地(de)来自(lái zì)这种(zhè zhǒng)内部(nèi bù)压力(yā lì)。

Pressurised balls have higher air pressure inside than outside, and more of their elasticity comes from that internal pressure.

这里(zhè lǐ)的(de)弹性(tán xìng)，就是(jiù shì)球(qiú)受力(shòu lì)改变(gǎi biàn)形状(xíng zhuàng)后(hòu)，能够(néng gòu)恢复(huī fù)的(de)性质(xìng zhì)。

Here, elasticity means the ball's ability to recover its shape after being deformed by a force.

它(tā)里面(lǐ miàn)的(de)气体(qì tǐ)处在(chǔ zài)大气压(dà qì yā)下(xià)，也就是(yě jiù shì)周围(zhōu wéi)空气(kōng qì)的(de)压力(yā lì)。

The air inside is at atmospheric pressure, meaning the pressure of the surrounding air.

它(tā)能够(néng gòu)弹(tán)起来(qǐ lái)，更(gèng)大(dà)的(de)一部分(yī bù fèn)原因(yuán yīn)在于(zài yú)橡胶(xiàng jiāo)内层(nèi céng)。

A larger share of its bounce comes from the rubber core.

这种(zhè zhǒng)球(qiú)的(de)橡胶(xiàng jiāo)内层(nèi céng)更(gèng)厚(hòu)，比(bǐ)加压(jiā yā)网球(wǎng qiú)更(gèng)依靠(yī kào)橡胶(xiàng jiāo)本身(běn shēn)的(de)弹性(tán xìng)。

Its rubber core is thicker, so it relies more on the rubber's own elasticity than a pressurised ball does.

不能(bù néng)把(bǎ)“无压(wú yā)”理解(lǐ jiě)成(chéng)没有(méi yǒu)空气(kōng qì)，也(yě)不能(bù néng)把(bǎ)回弹(huí tán)全(quán)归(guī)给(gěi)球(qiú)里面(lǐ miàn)的(de)气(qì)。

'Pressureless' does not mean airless, and the air inside does not account for all of a ball's bounce.