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What is called the moment of force? How to define it?

Let's try to find out what is called the moment of force. This term is often used in physics. The term under analysis is understood to mean the product of the shoulder and the force applied to it.

Features

Analyzing the question of what is called the moment of force, it is necessary to mention the unit of measurement of a given magnitude. In the international SI system, it is measured in Nm.

Rotational moment

The torque of a force relative to a point is the value associated with the shoulder and force. In everyday life, people often use the "rule of leverage", which is based precisely on the moment of force.

For example, in order to balance the scales-swing, you need to know what is called the moment of effort, and how to apply it correctly. The shoulder is the distance between the point of application and the point of rotation.

For example, it is problematic to open the door, pushing it against the fastening points. In order to understand why this is so difficult to do, you need to know what is called the moment of force relative to the axis.

Let's say that you need to open a door that has a meter width, attaching 100 N. To it, you need to apply it in three places:

  • Near loops;
  • In the center;
  • At the edge of the canvas.

For the first case, the shoulder will be zero, hence, the product of the shoulder force exerted will be zero.

For the variant on the center of the door, the moment will correspond to 50 Nm. For the lower part of the door leaf, the moment will have a maximum value of 100 Nm.

Such calculations allow us to conclude that the loss in distance is compensated by the gain in the effort.

Shoulder Rule

In the case of applying force at an angle, it is impossible to talk about the definition of the arm of forces as it was considered earlier. In order to cope with the task, it is necessary to use the rule of the shoulder. The shoulder of the force is the length of the perpendicular, which is lowered from the point of rotation to the line of action of the force.

In order to determine the shoulder strength, you need to lengthen the line. Then perpendicular from the point of rotation is lowered onto it.

The result is a triangle with right angles. Using the rules of trigonometry, you can determine the moment of force through the sine.

Assume that the force was applied at an angle of 45 degrees. In this case, the moment is 70 Nm. It becomes obvious that it will not be possible to open the door at an angle of 0 degrees. Such a force does not have a projection capable of causing rotational motion. The absence of her shoulder, other than zero, does not allow the force to create a torque. Reflecting on what is called the moment of power, it should be noted that this is a vector quantity. In order to determine the direction of the moment of force, use the rule of the right hand. The direction of the angular velocity vector is determined in a similar way .

What is the peculiarity of this rule? Cover the palm of the right hand axis of rotation, so that the direction of the fingers coincides with the direction of the applied force. The direction of the force moment vector is determined by the large finger. What is the moment of force relative to a fixed point? This is the value that connects the projection of the force moment vector and the axis about which the calculation will be performed.

The main moment of forces is a vector equal to the sum of all the moments of individual forces that act in the system with respect to the same point. It is called the center of bringing the whole system of forces.

In general, the result of the action on a rigid body of any system will be the same as the action of the main moment of the force system, as well as the force vector applied at the center of the reduction.

Conclusion

To describe the moment of forces, the basic law of dynamics, which characterizes rotational motion , is applied . He connects the moment of inertia, the angular acceleration, the moment of forces. After Archimedes established the rule of the lever, without any transformation, it was used almost 1900 years. Only in the second half of the 17th century the French scientist P. Varignon changed it and is connected with the moment of forces.

If the lever is in equilibrium, the equality M1 = M2 is observed. The moment of force is a characteristic of the rotational action of force. It depends not only on strength, but also on her shoulder. To unscrew the nut, use a long spanner. Screws much more quickly unscrew a screwdriver, which has a fairly long handle.

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