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当前位置:首页 > 教学参考> 学生园地> 趣味物理 > 内容详情

乒乓球中的物理知识

作者:未知  人气: 1335 次  时间:2017年11月06日  星级:

“从生活走向物理,从物理走向社会”是新课改的理念之一。乒乓球可以说是我国的国球,在各中小学普遍开展,是学生们喜爱的运动项目,下面就乒乓球运动项目中包含的物理知识作粗浅的分析。

乒乓球中的物理知识

一、乒乓球球台中的物理

1937年,国际乒乓球联合会对球台作了决定:球台长 274cm,宽152.5cm,离地面76cm。台面可用任何材料制成,但应是呈暗色、无光泽,而且要具有均匀一致的弹性。

“呈暗色,无光泽”:容易吸收光,不发生反光现象,且易与白色或黄色的乒乓球区分。

“均匀一致的弹性”:乒乓球落台后弹起发生下面能量转化,乒乓球的动能转化为弹性势能,又转化为乒乓球的动能。弹性材料易发生弹性形变而产生弹性势能。

二、乒乓球球拍中的物理

根据个人打球的风格不同,选择适合自己的球拍。不同的球拍物理性能不同。

1、摩擦力大,反弹力差的球拍。如反胶海绵拍,在海绵上贴一块颗粒向内的胶皮,由于表面平整柔软,有较大的粘性,在一定的作用(压力)下,摩擦力大,反弹力小。

2、弹性强,摩擦力较小的球拍。如生胶海绵拍,这种球拍是在较薄的海绵上贴一块生胶皮,其胶体的含胶量比正贴胶皮大,故颗粒比较柔软,弹力较大,颗粒的高度一般在0.8~1mm之间,易弹性形变,弹性强。

3、缓冲性能强的球拍。如防弧海绵拍,这种球拍是在一块结构松、弹力差的海绵上反贴一块厚而硬、粘性小,有些发涩的胶皮。由于结构松、弹力差,在力作用下易压缩,故缓冲性能强。

三、选择球的大小,软硬中的物理

1、采用大球,球性能的变化

自2000年10月使用40mm大球,其球的性能也发生一些变化。

(1)由于球体变大,其重量相应也增加(G=mg=vρg)。

(2)球体变大,空气相对球的阻力增大。运动物体受到空气的阻力跟其表面积有关,物体表面积越大,其空气阻力越大,由于空气中阻力的增大,使球运动的速度变缓。

(3)球体变大,空气阻力增大,减弱了球体的旋转、前冲。

2、赛前挑球。是乒乓球运动员的一个权力。硬一点的球,弹性好,打起来速度快;软一点的球摩擦力大,削起来容易旋转。

四、推挡球中的物理

1、挡球:球对拍一个作用力,同时球拍对球一个反作用力,从而改变球的运动状态。

2、快推:球与拍碰撞,接触时间越短,冲力越大,球获的较大速度。

3、加力推:反弹力与人施加的力同向叠加合成,力大球运动速度快。

4、减力挡:利用缓冲削弱反弹力。

五、球运行弧线、速度、旋转中的物理

1、球运行弧线的高低、长短、方向取决于击球时出手的角度、速度和力量。球运行作斜抛运动,击球时力的大小、方向、作用点三要素不同,力的作用效果不同,即球的运动状态不同。对于旋球来说球一方面自转,另一方面向前运动。

2、球的力量和速度

力作用球,是通过球前进速度和旋转强度表现出来,力越大球飞行越快或旋转越快,而击球力的大小,主要取决于击球时挥拍加速度的大小,由牛顿第二定律F=ma可解释。

3、上旋球。乒乓球的上旋,会使球体表面的空气形成一个环流,环流的方向与球体上旋方向一致,这时球体还在向前飞行,所以它同时又受到了空气的阻力。环流在球体上部的方向与空气阻力相反,在球体下部的方向与空气阻力一致,所以,球体上部空气的流速慢,而下部空气的流速快。流速慢的压强大,流速快的压强小。这样就使球体得到一个向下的力,这个力又让球得到一个加速度。我们把球体向前上方的运动看作这样两个运动的合成:一个是沿水平方向的匀速直线运动,另一个是竖直上抛运动。上旋球既可以携裹着强劲的力量和速度杀向对方,又能缩短打出的距离,增加乒乓球飞行弧线的高度。

运动员在削球或拉弧圈球时,球的线路会改变,道理同样运用了流体的压强跟流速的关系,由于乒乓球两侧空气的流动速度不一样,它们对球所产生的压强也不一样,于是,球在空气压力的作用下,被迫向空气流速大的一侧转变了。

六、乒乓球的压瘪与修复中的物理

1、压瘪:力可以使物体发生形变。

2、压瘪球的修复:压瘪的球压入热水中一段时间,会自动鼓起来,利用了物体热胀冷缩的道理。

总之,乒乓运动的产生和发展都是和力学、运动学紧密相联的,恰当地运用物理知识,球路变化一定能更得心应手。

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