RU2026572C1 - Position to conduct laboratory work in mechanism and molecular physics - Google Patents

Abstract

FIELD: training devices for physics. SUBSTANCE: position is provided with vertical pipe with through axial slots which is fixed with one butt in support with sockets and which other butt carries bracket where ends of filaments are anchored and bar with suspension and moved weight is suspended. Other ends of filaments are attached to support through pulling device and lever of first order which includes rod for discrete change of load with the use of weight, indicator of position of dial anchored in support. Transparent vessel filled with investigated fluid on which sliding rings are put is located in pipe. Plumb line with indicator is positioned along pipe. Support has adjustment screw, brackets with dropping device, capillaries and bar with devices for loading, reading and deformation of bending are installed in sockets. Filament carries bar with weights mounted for movement along it. EFFECT: improved convenience of operation, expanded operational capabilities. 1 dwg

Description

 The invention relates to educational devices in physics and can be used in laboratory work when studying the fluctuations of physical and mathematical pendulums, the moment of inertia, the parameters of tension and bending of materials, determining the viscosity of liquids by the Stokes method, studying the surface tension.

The closest in technical essence and the achieved effect is a workstation for a laboratory workshop, equipped with the following devices:
a device for studying the oscillations of the physical and mathematical pendulums, containing a pendulum made of a metal ball with a hook suspended from a suspension of thin thread in front of the clock with a second pendulum. The suspension consists of a steel prism mounted horizontally at the top of the watch. On the upper platform of the prism is a rod with a hole for securing the wire, which can be rotated and secured with a clamping screw;
a device for determining the moment of inertia, containing a thread with an investigated body suspended on it;
a device for determining the Young's modulus of tension, containing a thread fixed at one end to the bracket, and at the other end having a platform for accommodating goods and a reading device for the magnitude of the tension;
a device for determining the Young's modulus of bending, containing a rod, the ends of which are located on the supports, and in the middle is suspended a platform for placing load washers and a reading device for the amount of deflection;
a device for determining the viscosity of a liquid by the Stokes method, containing a long vertical transparent vessel with the test liquid, at the bottom and top of which there are marks, a set of balls of known density, a micrometer (vernier caliper) and a stopwatch;
a device for determining the surface tension of a liquid by the method of dropping drops and a method of capillaries containing a dropper with a known diameter of the outlet, a set of capillaries and a vessel for collecting droplets of liquid and filling with liquid when determining the coefficient of surface tension using capillaries (physical practice. M., State Publishing House, 1955 , 635 p.).

 The disadvantage of the equipment of such a workplace for a laboratory workshop is the inconvenience of operation, in addition, in the known devices there is no possibility of an operational change of the initial parameters.

 The aim of the present invention is to improve ease of use and expand operational capabilities by providing rapid changes in the initial parameters.

 This goal is achieved by the fact that the workplace for conducting a laboratory workshop on mechanics and molecular physics, containing a rod with a load, suspended on a prism for studying oscillations of physical and mathematical pendulums, the first thread with the body to be studied to determine the moment of inertia using torsional vibrations, the second thread and a second rod, mounted on brackets with a platform for placing goods to determine the Young's modulus of tension and bending, respectively, an indication system, an extended suck with marks, placed in the guiding device and filled with the studied fluid for determining the viscosity by the Stokes method, a dropper with a regulating device and replaceable capillaries for determining the surface tension coefficient of the fluid using the droplet separation method and the capillary method, made in the form of a single design, which is a vertically mounted tube with axial through slots, serving as a guide for the vessel with marks placed inside it, fixed by the lower end to the stand with sockets and adjusting elements horizontally and vertically, and having a curly bracket on the upper end to accommodate the threads and the rod with the load, the second ends of the threads are fixed to the stand, the first directly and the second through a lever of the first kind, in the sockets there are brackets fixed to them with a dropper and capillaries, while the lever of the first kind contains a rod for discrete changes in the load, and a millimeter scale and an indicator of location on the lever of the first kind, set Mounted with the ability to move relative to the scale mounted on the stand.

 Distinctive features of this decision are not known to the authors from the literature, which indicates that the solution meets the criterion of "significant differences".

 The drawing shows a General view of the workplace. It consists of a vertical pipe 1 with through axial slots 2, fixed at one end in a stand 3 by sockets 4, and at the other end having a curly bracket 5, in which the ends of the threads 6 and 7 are fixed and the rod 8 is suspended with a suspension 9 with a transported load 10. The other ends of the threads 6 and 7 are fixed on the stand 3 through the device 11 of the tension and the lever 12 of the first kind, containing a rod 13 for discrete changes in load 14 and a scale 15 for a smooth change of load using a sliding load 16, a position indicator 17 relative to the scale 18, is fixed oh on the stand 3. In the pipe 1 there is a transparent vessel 19 filled with the test liquid, on which the sliding rings 20 are located. Along the pipe there is a plumb line 21 with an index 22, the stand contains mounting screws 23, and in the sockets 4 there are brackets 24, 25 and 26, respectively with a drip device 27, capillaries 28 and a rod 29 with load devices 30 and reference 31, and bending strain. A rod 32 is attached to the thread with loads 33 having the ability to move along it.

 Before performing work using the adjusting screws 23 on the stand 3 and a plumb line 21 with an index 22, pipe 1 is aligned.

 Laboratory work is carried out as follows.

где l - длина стержня;
g - ускорение свободного падения. Далее на стержень 8 надевается груз 9, имеющий момент инерции ml_o ², где l_o - расстояние от центра масс груза до точки подвеса. Полный момент инерции физического маятника равен I = m(l² + l_o ²)/3. Если l_o = l, то I = = 2ml²/3. Груз помещается на различных расстояниях до точки подвеса, определяются периоды колебаний, строится и объясняется зависимость Т = f(l_o).1. The study of the physical and mathematical models of pendulums. A rod 8, which acts as a physical pendulum, is hung on the prism of the bracket 5, the period of its oscillations is determined, and compared with the theoretical value calculated by the formula
T _theor = 2π

where l is the length of the rod;
g is the acceleration of gravity. Next, a load 9 is put on the rod 8, having a moment of inertia ml _o ² , where l _o is the distance from the center of mass of the load to the suspension point. The total moment of inertia of the physical pendulum is I = m (l ² + l _o ² ) / 3. If l _o = l, then I = = 2ml ^2/3. The load is placed at various distances to the suspension point, the periods of oscillations are determined, the dependence T = f (l _o ) is built and explained.

При этом имеется ввиду, что масса стержня 8 по крайней мере в 10 раз меньше массы груза. Такая система стержень-груз считается моделью математического маятника. Имеются стержни различной длины (или массы), поэтому и исходные данные при выполнении работы разные.The oscillation period obtained in the case of securing the load 9 at the end of the rod 8 is compared with the theoretical calculated according to the formula for the mathematical pendulum
T = 2π

This implies that the mass of the rod 8 is at least 10 times less than the mass of the load. Such a rod-load system is considered a mathematical pendulum model. There are rods of various lengths (or masses), therefore, the initial data when performing work is different.

 2. The study of the moment of inertia using torsional vibrations is reduced to determining the maximum moment of inertia of the loads 33 and the moment of inertia relative to the central radial axis (strand 6).

- 1

где m - масса стержня 33, l - длина стержня.The moment of inertia of the rod 32 without loads 33 is determined by measuring the period of its oscillations, and then adding symmetrically to the thread 6 loads 33 and calculating by the formula
J =

- 1

where m is the mass of the rod 33, l is the length of the rod.

The obtained experimental value is compared with the theoretical value for the material point I = mr ² , where m is the mass of the load 33, r is the distance to the thread 6.

Then, the moment of inertia of the loads 33 is determined at different distances from the axis of rotation, and the dependence of the moment of inertia I on the distance r _о is built and analyzed.

 Using the tension device 11, the initial data is easily changed. Variations of the latter are supplemented by loads of various weights.

 3. Determination of the Young's modulus of tension reduces to determining the deformation of the yarn 7 under the action of discrete loads 14 put on the rod 13 of the lever of the first kind 12, or a smoothly variable load 16, determined on a scale of 15. The ratios of the shoulders of the lever are known, so the actual strains can be determined thread 7 using the reading device 17 and the scale 18.

 4. Young's modulus of bending is determined as follows. On the bracket 26 is placed the investigated cylindrical rod 29, on which the load device 30 is suspended, passing through the rod 31 with divisions. Discreetly change the amount of cargo and determine the corresponding strain.

где d - диаметр шарика, g - ускорение свободного падения;
ρ, ρ_o - плотность материала шарика и исследуемой жидкости;
l - расстояние между метками.5. To determine the viscosity of the fluid by the Stokes method, a ball of known diameter and density is lowered through the axial hole in the bracket 5, which enters the test fluid in the vessel 19. Through the slots 2 in the pipe 1, the time spent by the ball of marks 20 is recorded and the viscosity coefficient is calculated by the formula
η =

where d is the diameter of the ball, g is the acceleration of gravity;
ρ, ρ _o - the density of the material of the ball and the investigated fluid;
l is the distance between the marks.

 The initial data is changed due to the choice of material and size of the ball, as well as variations in the distance between the marks 20.

α_B где m - масса всех капель исследуемой жидкости,
m_В - масса такого же количества капель воды,
α_B - коэффициент поверхностного натяжения воды.6. The surface tension of liquids is determined by the method of separation of drops and using capillaries. In the first embodiment, the test fluid is poured into a vessel located on the bracket 24 in one of the sockets 4. Using the device 27, drops are separated from the capillary tube with an interval of 0.5-1 s, then the vessel is weighed with a known number of drops (the weight of the dry vessel is set). The experiment is repeated for water. The coefficient of surface tension is determined by the formula
α =

α _B where m is the mass of all drops of the test fluid,
m _In - the mass of the same number of drops of water,
α _B - surface tension coefficient of water.

 In the second embodiment, the surface tension coefficient is determined using capillaries 28 located on the bracket 25 in one of the sockets 4.

One of the capillaries 28 of a known section is placed in a vessel with the studied liquid, the height of the liquid raising in the capillary is measured, and the sought coefficient value is calculated by the formula
α = ρghr / 2 where ρ is the density of the liquid, r is the radius of the capillary, g is the acceleration of gravity.

 The initial parameters vary due to various capillaries of a known radius, changes in the properties of a liquid - due to the surface of active substances, task variations.

 Thus, the proposed design allows for greater ease of use, as well as quickly and widely change the initial parameters.

Claims (1)

 WORK PLACE FOR LABORATORY WORKS ON THE MECHANICS OF MOLECULAR PHYSICS, containing the first rod with a load suspended on a prism, for studying the oscillations of the physical and mathematical pendulums, the first thread with the body under study to determine the moment of inertia using torsional vibrations, the second thread and the second mounted on brackets with a platform for placing goods, to determine the Young's modulus of tension and bending, respectively, an indication system, an extended vessel with marks, fixed in the guide I’m using a device and filled with a test fluid for determining viscosity using the Stokes method, a dropper with adjusting elements and replaceable capillaries for determining the surface tension coefficient of a liquid by droplet separation and capillary method, characterized in that, in order to expand operational capabilities by providing operational changes in the initial parameters and increasing ease of operation, it is made in the form of a single design, which is a vertically mounted pipe with axial through slots, serving as a guide for the vessel with marks placed inside it, fixed with the bottom end on the stand with sockets and adjusting elements horizontally and vertically, and at the top end having a curly bracket for accommodating threads and rods with cargo, the second ends of the threads are fixed on the stand and the first one directly, and the second through the lever of the first kind, in the sockets there are brackets with a dropper and capillaries fixed to them, while the lever of the first kind contains a rod for discrete measurement changes in the load, a millimeter scale and an indicator of location on a lever of the first kind, mounted with the ability to move relative to the scale mounted on a stand, are used as an indicator device.

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