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Test questions 1. Explain the essence of the phenomenon of viscous friction. What is the nature of the internal friction forces of a fluid? Viscosity or internal friction is the property of fluid bodies (liquids and gases) to resist the movement of one part relative to another. This phenomenon determines the dissipation (absorption) of energy during deformation of the medium. During shear deformation, the viscosity is called shear viscosity. When the volume is deformed (universal compression), bulk viscosity appears. In this case, we will only touch upon the issue of shear viscosity. The essence of the phenomenon is that moving layers of gas or liquid entrain neighboring layers and, conversely, stationary layers (or moving at a lower speed) slow down faster neighboring layers. Thus, internal friction forces (or viscous forces) act between any adjacent layers of the medium under consideration. The mechanism by which these forces arise is the transfer of momentum (amount of motion) from one layer to another.2. What is the coefficient of dynamic viscosity? In what units is viscosity measured in the SI system?
The coefficient of dynamic viscosity is a value numerically equal to the force of internal friction with which one layer drags or slows down another layer of liquid, provided that the contact area of the layers and the velocity gradient . In the SI system, the unit of dynamic viscosity is taken to be the viscosity of a medium in which one layer drags or inhibits another with a force of , if the contact area of the layers and the velocity gradient are .
3. What forces act on a body moving in a liquid?
A body immersed in a liquid and remaining in equilibrium afloat is acted upon by two forces: the force of gravity and the buoyant force equal to it (and equal to the weight of the liquid displaced by the immersed volume of the body). Three forces act on a body immersed in a liquid and sinking: the force of gravity, which is unequal to it (less), the buoyancy force (equal to the weight of the liquid displaced by the immersed volume of the body), as well as the frictional force during movement, which largely depends on the speed of immersion and the viscosity of the liquid . A body immersed in a liquid and lying tightly at the bottom is acted upon by three forces: the force of gravity, the unequal buoyant force, and the reaction force from the bottom. In this case, the buoyant force decreases by an amount equal to the weight of the liquid occupied by that part of the body volume under which there is no water
4. Define laminar and turbulent fluid flow.
Turbulent flow is a fluid flow in which its particles perform unsteady and disordered movements along complex trajectories, leading to mixing of layers. Laminar is an ordered flow of fluid in which the trajectories of motion of neighboring particles differ little from each other.
5. Write down the Stokes formula and indicate the conditions for its applicability.
For spherical bodies, the modulus of the viscous friction force is determined by the Stokes formula (1) where r is the radius of the ball; V is the speed of its movement relative to the liquid. It is important to note that formula (1) is valid only in the case of laminar fluid flow relative to the ball (the speed of the ball should be small), and the fluid extends infinitely in all directions, i.e. The dimensions of the vessel in which the liquid is located must be much larger compared to the dimensions of the ball.
6. Determine the magnitude of the friction force acting on a steel ball with a diameter of 3 mm falling at a speed of 0.75 m/s in a liquid with a viscosity coefficient of 1.5 Pa.s. F=6*3.14*1.5*0.003*0.75=0.063
7. Why does the ball accelerate at the beginning of its movement and then move uniformly? What is a velocity gradient? At the beginning of the ball's movement, the movement will be accelerated due to the acceleration of gravity. As the speed increases, the resistance force also increases, and the acceleration of the ball decreases. There comes a moment when the forces acting on the ball are balanced, the acceleration becomes zero, and the movement of the ball becomes uniform in section L. The velocity gradient is the change in the speed of two layers of liquid dV at the distance between the layers dX.
8. Write down the working formula, explain the conditions for its use and the reason for starting to measure time not from the surface of the liquid.
The upper mark is placed several centimeters below the upper level of the liquid to ensure uniform movement of the ball in the liquid. 9. List the main sources of measurement errors carried out in this work.
Concept, essence and structure of psychological climate
The concept of “climate” has roots in social psychology. This term, now widely used, is often put on a par with the concepts of spiritual atmosphere, team spirit and prevailing mood. In Russian psychology, four main approaches to understanding the nature of the SPC have emerged.
Representatives of the first approach (L.P. Bueva, E.S. Kuzmin, NH Obozov, K.K. Platonov, A.K. Uledov) consider climate as a socio-psychological phenomenon, as a state of collective consciousness. Climate is understood as a reflection in the minds of people of a complex of phenomena related to their relationships, working conditions, and methods of stimulating it.
By socio-psychological climate, E. S. Kuzmin believes, it is necessary to understand such a socio-psychological state of a small group that reflects the nature, content and direction of the real psychology of the organization's members.
Proponents of the second approach (A.A. Rusalinova, A.N. Lutoshkin) emphasize that the essential characteristic of the socio-psychological climate is the general emotional and psychological mood. Climate is understood as the mood of a group of people.
The authors of the third approach (V.M. Shepel, V.A. Pokrovsky, B.D. Parygin) analyze the socio-psychological climate through the style of relationships between people who are in direct contact with each other. In the process of formation, a system of interpersonal relationships is formed that determines the social and psychological well-being of each member of the group.
The creators of the fourth approach (V.V. Kosolapov, A.N. Shcherban, L.N. Kogan) define climate in terms of social and psychological compatibility of group members, their moral unity, cohesion, the presence of common opinions, customs and traditions [3].
In American social psychology they talk about “organizational culture” in organizations, about the relationship between workers and managers. E. Mayo's theory of “human relations” is based primarily on the formation of the socio-psychological climate of relations between employees.
When studying climate, it is necessary to keep in mind two levels.
The first level is static, relatively constant. These are stable relationships among team members, their interest in work and fellow workers. At this level, the socio-psychological climate is understood as a stable, fairly stable state, which, once formed, is capable of not being destroyed for a long time and maintaining its essence, despite the difficulties that the organization faces. From this point of view, it is quite difficult to create a favorable climate in a group, but at the same time it is easier to maintain it at a certain level, already formed earlier. Control and correction of the properties of the socio-psychological climate are carried out by group members occasionally. They feel a certain stability, stability of their position, status in the system of relationships. Since the state of the climate is less sensitive to various influences and changes from the environment, it has a real impact on the results of collective and individual activities, on the performance of group members, on the quality and quantity of the products of their labor.
The second level is dynamic, changing, fluctuating. This is the daily mood of employees during work, their psychological mood. This level is described by the concept of “psychological atmosphere”. In contrast to the socio-psychological climate, the psychological atmosphere is characterized by more rapid, temporary changes and is less recognized by people.
Changes in the psychological atmosphere affect the mood and performance of the individual during the working day. Climate changes are always more pronounced, noticeable, they are realized and experienced by people more acutely; most often a person manages to adapt to them. The accumulation of quantitative changes in the psychological atmosphere leads to its transition to a different qualitative state, to a different socio-psychological climate.
K. Argyris, based on his research on climate in a bank, gave it the following definition: “the official policy of the organization, the needs of employees, values and individuality that operate in a self-preserving complex, living and constantly evolving system.” Now the concept of “climate” is understood as the organizational influence on the motivation and behavior of employees, i.e. it includes aspects such as organizational structure, reward systems, and the perceived support and friendly participation of managers and colleagues. Climate refers to the team's overall view of organizational policies, activities, and events, both formal and informal. In addition, climate is the clear goals of the organization and the means used to achieve it [16].
The climate of the collective is the prevailing and relatively stable mental mood of the collective, which finds diverse forms of manifestation in all its life activities.
The socio-psychological climate of a team is always characterized by an atmosphere specific to the joint activities of people, the mental and emotional state of each participant, individual, and undoubtedly depends on the general state of the people around him. In a production team, various relationships develop between employees, including moral ones. As a result, the image of the team becomes dependent on personal qualities: honesty, decency, dedication. In turn, the atmosphere of a particular community or group is manifested through the nature of the mental mood of people, which can be active or contemplative, cheerful or pessimistic, purposeful or anarchic, everyday or festive, etc.
An essential element in the general concept of socio-psychological climate is the characteristics of its structure. Not only in sociology, but also in psychology, the point of view has been established, according to which the main structure that forms the socio-psychological climate is mood.
In the structure of the socio-psychological climate, there are two main divisions:
- people’s attitudes towards work;
- their relationship to each other.
In turn, relationships with each other are differentiated into relationships between workmates and relationships in the system of leadership and subordination.
Ultimately, the entire diversity of relationships is viewed through the prism of two main parameters of the mental mood - emotional and objective.
The psychological climate of the collective, which reveals itself primarily in the relationships of people to each other and to the common cause, is still not exhausted by this. It inevitably affects people’s attitudes towards the world as a whole, their attitude and worldview. And this, in turn, can manifest itself in the entire system of value orientations of an individual who is a member of a given team. Thus, climate manifests itself in a certain way in the attitude of each member of the team to himself. The last of the relationships crystallizes into a certain situation - a social form of self-attitude and self-awareness of the individual.
As a result, a certain structure of immediate and subsequent, more immediate and more indirect manifestations of the socio-psychological climate is created
