OBJECTIVETo resolve the contradictory in expounding of reinforcing and reducing by lifting and thrustion the needle and slow-rapid reinforcing and reducing method.

METHODSIn a certain condition,the relationship between the external force (the joint force of both the pressing on the force pressing on the needle and the force arresting the needle's moving) and the speed of needle's moving is deduced by means of kinetic energy theorem, so, when the needle is heavily thrust or lifted, the speed of its moving will be increased.

CONCLUSIONIn the reinforcing and reducing method by lifting and thrusting the needle, "heavily"and "gently" of heavily thrustiing and gently lifting or gently thrusting and heavily lifting should be considered as differences of the amplitudes of lifting and thrusting the needle; "slow-rapid" of slow-rapid reinforcing and reducing method should be considered as difference of the speeds.