Simple mechanisms

Learning objectives

What are called simple mechanisms.
What can be won with simple mechanisms, what can't be won.

Warm-up

In order to transport the stones out of the mines, the builders of the pyramids had to lift them onto pallets. The stones themselves weighed an average of 2,300 kilograms, but there were also weights of 14,000 kilograms. How could such stones be lifted without machines, lifting blocks and all kinds of wheeled equipment?

Simple mechanisms?

Simple mechanisms and the golden rule of mechanics

Let's try it

Lever

Along the ramp

Let's try

Summary

Simple mechanisms are devices with a simple construction (without a motor) that change the size or direction of the transmitted force. If we place a long rigid rod on the fulcrum, we have obtained a simple mechanism called a lever.

Simple mechanisms do not change the amount of work that needs to be done. A simple mechanism changes the required force and the distance traveled. As many times as you gain in strength when using a simple mechanism, you lose in the length of the path traveled, and vice versa.

How much of the work done is useful work is shown by the efficiency factor. Total work is always greater than useful work, because in addition to doing work, we have to spend to overcome various hindering forces. The ratio of useful work to total work is called the efficiency factor:

Kasutegur = \frac{kasulik t ¨ o ¨ o}{kogut ¨ o ¨ o}

In most cases, the efficiency is given as a percentage:

η = \frac{A_{k a s}}{A_{k o g u}} \cdot 100 %

The shoulder of the force $l$ is the distance from the center of the lever to the point of application of the force. The lever rule, or the lever balance condition, can be written with a formula

F_{1} \cdot l_{1} = F_{2} \cdot l_{2}

The balance condition of a lever says that if one force arm of the lever is a certain number of times longer than the other, then the same number of times less force can be applied to it, so that the lever remains in balance.

Control questions

Additional materials

Here we find out

Would you build a pyramid?