Ball screw is dedicated to the turning of thread and setting, in the other surface is turning, light, not only its poles ball screw.

丝杠是专门用来车削各种螺纹而设置的，在进行工件的其他表面车削时，只用光杠，不用丝杠。

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To state the restoring force of a simple pendulum during oscillation is the resultant force of the gravity of the ball and the pulling force of the thread is wrong .

常出现一些模糊认识，即认为单摆在振动中所受的回复力就是摆球所受重力与绳子拉力的合力，显然，这是错误的。

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So Tom unwound the thread from one of his needles, and each boy pricked the ball of his thumb and squeezed out a drop of blood.

31于是汤姆拿出一根针，去掉了线。两个孩子各自往大拇指上戳了一下，然后挤出两滴血来。

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So Tom unwound the thread from one of his needles, and each boy pricked the ball of his thumb and squeezed out a drop of blood.

31于是汤姆拿出一根针，去掉了线。两个孩子各自往大拇指上戳了一下，然后挤出两滴血来。

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