对于一个在地面上滚动的球而言，外力可能是球与地面之间的摩擦力或者幼童相反方向踢球产生的力。
For a ball rolling across the floor, that outside force could be the friction between the ball and the floor, or it could be the toddler that kicks the ball in another direction.
这项研究表明，脚和球之间的摩擦系数的增加导致了球获得更多的角动能。
This study showed that an increase in the coefficient of friction between the ball and the foot caused the ball to acquire more spin.
滚动托料球，减少板料划伤，并可减少摩擦阻力。
Rolling material support ball is set, to minimize fish tail with sheet bar and to reduce frictional resistance.
此有效摩擦系数被应用于研究刚性球自由斜冲击延性靶问题。
The effective friction coefficient is applied to the study of the oblique impact of a rigid sphere against a ductile solid.
文中采用传统的四球机法，对工投牌高扭矩钻具螺纹脂的摩擦系数进行了测试。
The paper measures the friction coefficient of Gongtou brand thread compounds for high torque drill tool.
摩擦力使滚动的球最终停了下来。
该装置通过八个钢球利用摩擦力将动力进行输入输出，用一对斜齿轮进行分度调速，从而使自行车在0.75～1.22之间进行无级调速。
They are used to input or output the power through the friction and a pair of helical gears is also used to adjust the speed, so the speed can change between 0.75 and 1.22.
通过四球试验，考察了软金属微米铜粉在润滑脂中的摩擦学行为和抗磨性。
The tribological properties and the anti-wear of micron coppers inside greases were investigated by four-ball test.
利用球盘磨损试验机和电化学综合测试仪研究了IBED膜层的摩擦学性能和电化学腐蚀特性。
The wear resistance and electrochemical corrosion properties of IBED coatings were investigated with ball-on-disk wear tester and electrochemical equipment, respectively.
离合器摩擦片的压紧是由钢球在离心力作用下沿斜面滚道向外滚动而引起的。
The clamping of the friction disk is caused by the outwardly rolling of the steel ball along the slop rolling track under eccentric force.
四球试验结果表明，该悬浮液具有较好的极压性能，抗磨性能一般，MTM试验显示该悬浮液对摩擦系数影响不大。
The four-ball machine test showed that the suspension possessed good extreme pressure performance and common antiwear performance; and had no effect on the friction coefficient by the MTM test.
用摄动法分析刚球在非线性滑动摩擦力作用下的运动规律。
The perturbation method is used to analyse the motion of the rigid sphere under the action of the nonlinear sliding friction.
大量的研究表明，柱塞与滑靴之间的球铰副摩擦力很大程度上影响着轴向柱塞泵的性能及寿命。
A lot of study showed that the friction of the ball friction coupling between piston and slipper obviously affected the life-span and the performance of the axial piston pump.
另外，在四球试验机上考察了铅纳米晶的摩擦学性能。
In addition, the tribological properties of nanocrystalline Pb powders were tested with a four-ball machine.
通过四球试验 ，考察了软金属微米铜粉在润滑脂中的摩擦学行为和抗磨性。
The tribological properties and the anti-wear of micron copper powder in greases are investigated by four-ball test.
通过四球试验，考察了微米铜粉在润滑脂中的摩擦学行为和抗磨性。
The tribological properties and the anti-wear of micron coppers inside greases were investigated by four-ball test.
通过四球试验，考察了微米铜粉在润滑脂中的摩擦学行为和抗磨性。
The tribological properties and the anti-wear of micron copper powder in greases are investigated by four-ball test.
通过四球试验，考察了微米铜粉在润滑脂中的摩擦学行为和抗磨性。
The self - repair performance of micron copper in grease is evaluated with four - ball tester.
本发明提高了球和鞋表的接触面积，增加了摩擦力，穿着具有较好的适应性和弹性。
The invention increases the contact area between the football and the shoe surface, increases the friction and has an adaptive and flexible wearing.
本发明提高了球和鞋表的接触面积，增加了摩擦力，穿着具有较好的适应性和弹性。
The invention increases the contact area between the football and the shoe surface, increases the friction and has an adaptive and flexible wearing.
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