求翻译：密度，指单位体积的重量，在拍形、厚度相对固定的情况下，可用重量代换。根据动能定理和牛顿第二定律，重量大者动能大，击球后反弹速度快，利于短距离弹击或被动击球，但不利于加速，高速变向也因动能(惯性)大而变得困难。随着直拍横打和弧圈技术的发展，正反面双贴胶皮已呈绝对主流，胶皮重量的增加，大幅提高了底板 floor的轻量化要求。是什么意思？

Density refers to the weight of unit volume, shot shape, thickness is relatively fixed, the available weight of substitution. According to the theorem of kinetic energy and Newton's second law, the weight of the kinetic energy, rebound fast after hitting the ball, which will help the short-range she

Density refers to the weight per unit of volume, in a relatively fixed shape, thickness, weight available for generation. Based on kinetic energy theorems 2 and Newton's law, the weight of a kinetic energy of the ball, after fast anti-pop-pop-ups, and beneficial for short distances or passive shot,

The density, refers to the unit volume the weight, in pats in the shape, the thickness relatively fixed situation, available weight substitution.According to the kinetic energy theorem and the Newton second law, the weight big kinetic energy is big, after hits a ball the resilience speed to be quick

Density, weight per unit of volume, in the case of relatively fixed shape, thickness, weight substitution available. According to kinetic energy theorem and Newton's second law, weights, kinetic energy, after hitting the rebound speed fastest, hitting the bombs hit to short distances, or passive, bu

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