Weight is measured with scales, distance with a ruler, pressure with a manometer, etc. Has a device been invented that measures force? Such a tool certainly exists. It's called a dynamometer. With your own hands at home, by the way, it is easy to make a simple but quite efficient device for measuring force, your own exclusive dynamometer.
Mass, force, weight
In conversations, we often confuse concepts such as mass and weight. What is the difference between them? Small example. We have a gymnastic kettlebell weighing 32 kg. This is how much our household scales will show, if we put this iron product on them. Let's move mentally to the surface of the moon. The readings of the scales that we will take with us will change and will be only 5 kg 120 g. But on the largest planet in our system, Jupiter, with the greatest gravity, the scales will show all 84.5 kg. Has the mass of the kettlebell changed? No.
How can this be? Let's place a weight in outer space, where in a state of weightlessness the scales will show zero at all. Is the weight gone? To make sure that this is not the case, it is worth dispersing our gymnastic apparatus to a decent speed and directing it to one or another target. If the same experiment is repeated on the Moon, Earth, Jupiter, provided that the speedat the moment of collision with an obstacle will be the same, the destruction will be identical.
The mass of the kettlebell in all examples remains 32 kg. What is changing? The force with which the weight presses on the platform of the balance. And to measure it, this force, called "weight", is correct not in kilograms, but in newtons.
A force of one newton is equal to the weight of a load of 102 grams on the surface of the planet Earth.
So, having made a dynamometer with our own hands, we will be able to measure such an important physical quantity as force.
General principle of dynamometer design
Gravity is rarely used to measure force. This is not only inconvenient (a weight or counterweight can only work vertically), but also not entirely accurate. The fact is that our Earth is not quite a sphere. It is an ellipsoid, slightly flattened at the poles. Therefore, the distance at the equator to the center of the planet is greater than at the pole, in addition, at the equator, any body is affected by centrifugal force, which slightly reduces its weight, so in order to be guaranteed to lose weight (albeit not much, by 0.5% only), you just need to go from the pole to the equator.
Therefore, in order to measure force, devices on elastic elements are most often used. And sometimes it is necessary to measure a force that is simply enormous, for example, the thrust of the engine of a space carrier rocket. One can only imagine what such a dynamometer should be like.
You can hardly make one with your own hands. But the principle of operation for all "power meters" is the same: the forcedeforms the elastic element, the device fixes the value of this deformation.
Standard Dynamometer
In the laboratory work of school physics lessons, a simple spring device was used to measure force. Consider how to make a dynamometer with your own hands no worse than a school one.
The basis on which the entire device is assembled is an ordinary plank of wood or a strip of polycarbonate, plastic, tin, there are many options. There is a spring on the plate, one end of which is rigidly fixed, the other is connected to the body through which the force is transmitted. As a rule, this is a steel hook. The extent to which the spring is stretched is proportional to the applied force. The amount of deformation is reflected on the scale, which is applied in newtons. This is how a dynamometer works. With your own hands at home, it is not necessary to make it from a spring, any elastic material, for example, an elastic band, will work fine.
Calibration
In order for the force meter to work, it must be calibrated. You can use gravity to do this. It is known that a force of one newton corresponds to a weight of 102 grams. The dynamometer is calibrated with your own hands in the following sequence:
- dynamometer is vertical;
- while the spring is not loaded, the pointer position corresponds to 0;
- dynamometer is loaded with a weight of 102 grams, the mark is 1 newton;
- a weight of 204 grams will give a mark position of 2 newtons, etc.
As you can see, set upDIY dynamometer is easy.
Different designs of "home" dynamometers
It is necessary to decide on the load to be measured. And it is better to make a calculation before making a dynamometer. With your own hands, you can make both a powerful device and a small, but more sensitive one. And there are many design options.
For example, it is easy to make a dynamometer with your own hands from rubber. It is no different from the classic "school". The only difference is that instead of a spring, a more affordable elastic band is used, for example, from a bottom fishing rod or model aircraft.
With a little imagination, an ordinary disposable syringe turns into a device for measuring strength. The device is shown in the figure, the only thing to focus on is the syringe plunger, which must be turned around (or cut with a sharp knife) so that it moves inside the syringe body without effort.
If you wish, you can make a dynamometer with your own hands from a pen, an ordinary ballpoint pen with a spring.
The rod must be cleaned of ink, grind off the tip of the writing ball and insert an ordinary paper clip inside.
Dynamometer on piezoelectric elements
Prefabricated dynamometers in recent times are most often made using piezoelectric elements. Piezoelectric element - crystal, at the endswhich, during mechanical compression, a potential difference (voltage) appears. Moreover, the magnitude of this potential difference depends on the degree of compression.
Dynamometers of this type are distinguished by the absence of a rod stroke (you just need to press the sensitive element), extreme accuracy and a huge measurement range. Piezoelectric elements are used to make both sensitive devices for accurately measuring small forces, and dynamometers, which measure the tractive forces of tractors.
