Modern Physics

What is the lever arm?

The lever arm is the existing perpendicular distance from the axis of rotation to the line of action of the force. The magnitude established for the study of this process is τ = N m. The lever arm is related to the torque present at a specific point.

The distance established by the lever arm works as a force amplification factor, as seen in levers in general.

This relationship finally creates torque and can be plotted by extending a line of force action along with a perpendicular line coming from the point of rotation to create a right angle.

What is a lever?

A lever is defined as a machine whose function is to transfer force and displacement to increase the mechanical force, speed or distance covered by a rigid bar.

To express the movement made by a lever, physical elements such as force (represented by an “F”), force (represented by an “P”) and resistance (represented by an “R”) are used.

There are three types of levers: first, second and third degree levers.

1st degree lever

The first degree lever is the one in which the fulcrum is between resistance and power. The latter can be less than resistance. A clear example of this type of lever would be scissors, rocker arms or pliers.

second degree lever

The first degree lever is one where resistance can be placed between fulcrum and force. In that case, the latter will always be less than the resistance.

A clear example of this type of lever would be a boat oar, a nutcracker and even a cart.

Third grade lever

The first degree lever is one where power can be found between fulcrum and resistance. A characteristic of this type of lever is that the applied force is much greater than the net force.

An example of this type of lever would be a fishing rod, staple removers and even the temporomandibular joint of a person or animal.

How to calculate the lever arm?

The lever arm often appears frequently when you want to perform a torque calculation. To perform this procedure, it is first necessary to determine the lever arm and then multiply it by the applied force.

As we said before, the lever arm is the present perpendicular distance between the axis of rotation and the line of action of the force.

The initial equation would be:

Torque over a spanner = force lever arm X.

The equation to determine the lever arm is:

Lever arm = r SenѲ.

From then on, it is only necessary to release the lever arm to determine its magnitude.

You can also calculate the lever arm in a slightly more general situation rather than a physical problem.

For this, it is necessary to observe the force applied to the body or object and, therefore, consider the existence of a line perpendicular to the force being applied and which is crossing the point of interest that we want to determine.

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