Moment is a physical quantity that exerts a rotating effect on an object. It can be divided into the moment to the axis and the moment to the point. Namely: M=LxF. Where l is the distance vector from the axis of rotation to the focus, f is the vector force, and torque is also the vector.

The vertical distance from the line of action of the arm to the axis of rotation. The arm of force corresponding to power is called power arm, and the arm of force corresponding to resistance is called resistance arm.

Second, the nature is different.

Characteristics of torque

1, the moment of force F to point O is not only determined by the force, but also related to the position of the moment center. The moment varies with the position of the moment center;

2. When the force is zero or the arm is zero, the moment is zero;

3. When the force moves along the line of action, the moment remains unchanged, because the magnitude, direction and arm of the force have not changed.

4. The algebraic sum of the moments of two forces that are balanced at the same point is equal to zero.

Properties of arm of force

1, the moment arm is the distance from the fulcrum to the line of force action, and the mathematical model of the moment arm is the distance from the point to the straight line. Where the "point" is the fulcrum of the lever; "Line" is the line of action of force, that is, a straight line drawn along the direction of force through the point of action of force. It should be noted that the moment arm can never be understood as "the length from the fulcrum to the stress point".

2. If the directions of several forces acting on the same point are different, the arm of force is generally different.

3. If the line of action of force passes through the fulcrum, then the arm of force must be zero.

Third, the application is different.

Application of torque

The application of torque is motor. The so-called torque motor is a flat multipole permanent magnet DC motor. Its armature has more slots, commutator and series conductor to reduce torque fluctuation and speed fluctuation. There are two kinds of torque motors: DC torque motors and AC torque motors.

Application of force arm

Bicycle is a combination of simple machinery in structure, and it can walk by applying the principle of mechanical balance when driving.

1. The handlebar is a labor-saving lever when rotating, which can save labor when the power arm is larger than the resistance arm.

2. The brake is a lever when used, which can save labor when the power arm is larger than the resistance arm.

3. The pedal and the big flywheel, and the small flywheel and the rear wheel form the axle device. The power can save effort when acting on the wheel, but it is laborious when acting on the axle.

Wire cutters are made by using the principle of labor-saving lever.

1, cutting, under the same stress, the cutting area is small, which can increase the pressure of cutting iron wire.

2. The whole fixture is a labor-saving lever, which can save labor.

3, plastic handle, concave and convex surface patterns, can increase the beneficial friction.

4, plastic handle is insulating plastic, which can prevent electric shock accidents.

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