closed system

Examples of closed system in the following topics:

• Work

  • Work performed by a closed system is the energy transferred to another system that is measured by mechanical constraints on the system.
  • In thermodynamics, work performed by a closed system is the energy transferred to another system that is measured by mechanical constraints on the system .
  • For closed systems, energy changes in a system other than as work transfer are as heat.
  • Heat transfer into a system, such as when the Sun warms the air in a bicycle tire, can increase its temperature, and so can work done on the system, as when the bicyclist pumps air into the tire.
  • However, both can change the internal energy of a system.

• Rotational Collisions

  • In a closed system, angular momentum is conserved in a similar fashion as linear momentum.
  • During a collision of objects in a closed system, momentum is always conserved.
  • So rotating objects that collide in a closed system conserve not only linear momentum p in all directions, but also angular momentum L in all directions.
  • After the collision, the arrow sticks to the rolling cylinder and the system has a net angular momentum equal to the original angular momentum of the arrow before the collision.

• Momentum, Force, and Newton's Second Law

  • In a closed system (one that does not exchange any matter with the outside and is not acted on by outside forces), the total momentum is constant .
  • If the mass of the system is constant, then Δ(mv)=mΔv.
  • Because Δv/Δt=a, we get the familiar equation $F_{net} = ma$ when the mass of the system is constant.
  • Newton's second law of motion stated in terms of momentum is more generally applicable because it can be applied to systems where the mass is changing, such as rockets, as well as to systems of constant mass.
  • In a game of pool, the system of entire balls can be considered a closed system.

• Conservation of Angular Momentum

  • A closed system is involved.
  • They are isolated from rotation changing influences (hence the term "closed system").
  • There appears to be a numerical quantity for measuring rotational motion such that the total amount of that quantity remains constant in a closed system.
  • The net torque on her is very close to zero, because 1) there is relatively little friction between her skates and the ice, and 2) the friction is exerted very close to the pivot point.

• Pressure in the Body

  • Pressure plays an essential role in various critical bodily systems that are necessary for survival.
  • One such critical bodily system which relies on pressure for functionality is the circulatory system, which is an example of a closed fluid system under pressure.
  • Blood can be regarded as a viscous liquid contained within the circulatory system that travels throughout this closed system as a result of pressure and pressure differences within the circulatory system.
  • As the volume of blood within the circulatory system is confined to the veins, arteries, and capillaries there is a pressure within this closed system.
  • Explain role played by pressure in the circulatory and respiratory systems

• The First Law

  • The 1st law of thermodynamics states that internal energy change of a system equals net heat transfer minus net work done by the system.
  • It is usually formulated by stating that the change in the internal energy of a closed system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings.
  • Here ΔU is the change in internal energy U of the system, Q is the net heat transferred into the system, and W is the net work done by the system.
  • So positive Q adds energy to the system and positive W takes energy from the system.
  • W is the total work done on and by the system.

• Conservative and Nonconservative Forces

  • Instead, they transfer the energy from the system in an energy form which can not be used by the force to transfer it back to the object in motion.
  • Work done by the gravity in a closed path motion is zero.
  • We can extend this observation to other conservative force systems as well.
  • We imagine a closed path motion.
  • We imagine this closed path motion be divided in two motions between points A and B as diagramed in Fig 1 .

• Internal Energy

  • The internal energy of a system is the sum of all kinetic and potential energy in a system.
  • However, a system does contain a quantifiable amount of energy called the internal energy of a system.
  • It is closely related to temperature.
  • Q is heat added to a system and Wmech is the mechanical work performed by the surroundings due to pressure or volume changes in the system.
  • We can calculate a small change in internal energy of the system by considering the infinitesimal amount of heat δQ added to the system minus the infinitesimal amount of work δW done by the system:

• Constant Pressure and Volume

  • In other words, the system is dynamically connected, by a movable boundary, to a constant-pressure reservoir.
  • If a gas is to expand at a constant pressure, heat should be transferred into the system at a certain rate.
  • It follows that, for the simple system of two dimensions, any heat energy transferred to the system externally will be absorbed as internal energy.
  • An example would be to place a closed tin can containing only air into a fire.
  • We may say that the system is dynamically insulated, by a rigid boundary, from the environment.

• Standing Waves in Air Columns

  • At the closed end, there is no displacement; this is called a node, and the air is halted.
  • We use specific terms for the resonances in any system.
  • The resonant frequencies of a tube closed at one end are:
  • The fundamental and three lowest overtones for a tube closed at one end.
  • All have maximum air displacements at the open end and none at the closed end.