网球击中地面后弹回到空中 - 也就是球反弹在比赛中球的反弹力会越来越弱需要换新球
When a tennis ball hits the ground and bounces back into the air - that is, the ball bounces back. During the game, the rebound force of the ball will become weaker and weaker, and a new ball needs to be replaced
以上为机器翻译结果，长、整句建议使用 人工翻译 。