Each lever has its own – the flag

The weekend in Ascension was rich with sporting events that made headlines, both in rugby and football. Besides the controversies that followed these matches, it is an opportunity to illustrate a very common physical phenomenon. What is the common point between perforating banknotes
At the entrance to the stadium, when you open a bottle of beer and a good shot the goal to win a contested match?

In physics, the purpose of a lever is to transmit force through a fixed point called an axle. The principle of the lever was discovered a very long time ago, and by looking around we can quickly identify many examples of levers everywhere.

They are classified into three types:

Cranes of the first type are those that naturally come to mind. For this class, the hub is placed between the two voltage points. This principle is used on pliers, scales, swings, scissors, etc. The force transmitted depends on the applied force and the distance between the point of application and the axis. For a certain effort, the more force is applied to the axle, the less it is needed, but the movement of the lever will be greater, so the force will act over a greater distance.

– On winches of the second type, the axle is placed at one end of the winch. Since the force needed decreases with distance from the axle, it is known that a force applied at the end of the lever will always make it possible to obtain a greater force at a closer distance from the axle. But this effort will be applied over a shorter distance. It is this type of lever that is implemented, for example, on wheelbarrows, where the wheel is the axle. With bottle openers too, a great force is applied by making a great movement at the end of the handle, but at a limited distance on the capsule to the point of ejecting it from the bottle.

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Finally, there are levers of the third kind. Again, the axle is at the end of the lever, but force is applied close to the axle. The benefit is to apply a certain force over a small distance, to move the end of the lever a large distance. The typical example of this lever is the leg of a rugby player executing a penalty kick: the pivot is the hip, the muscles exert force in the upper part of the leg, and then the lower part of it moves very quickly to hit the ball and send it to the goal!

Malo de Brito

News Issue 148 – June 8, 2022

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