In physics, a system is defined as the portion of the universe that has been chosen for study. Systems may be complex, such as a whole planet, or simple, such as the water inside a pot. The universe outside the system is called the surroundings. A closed system is one that does not exchange matter with its surroundings and does not experience any outside forces. An open system, on the other hand, can exchange matter with its surroundings and does experience outside forces.
The idea of systems and surroundings was not always part of physics. In 1824, the French physicist Nicolas Carnot applied the idea of systems to thermodynamics. A little later, German physicist Rudolf Clausius added the idea of surroundings. Today, system and surroundings are terms applied also to mechanical systems, as well as used in other scientific fields such as biology.
Examples of open systems are common in everyday life. A car driving down a road is a system. The car engine produces exhaust, which is matter passed to its surroundings. Friction between the car and the road is an outside force that acts on the system. Closed systems are rare in everyday life. They are commonly used in physics laboratories to simplify system analysis and calculations.
So, what questions can help someone decide whether the system under consideration is open or closed? The first question to ask is: Does the system exchange matter with its surroundings? If yes, it is an open system. If no, it is a closed system. The second question is: What is the source of the forces experienced by the system? If all forces originate within the system, the system is closed. If forces act on the system from outside of the system, it is an open system.
QUESTION 1
A student has chosen to study a swinging pendulum. The pendulum would be ____________.
OPTIONS
a system
the surroundings
a universe
a force
QUESTION 2
Which of the following statements describes a closed system?
OPTIONS
It exchanges matter with its surroundings.
Its surroundings act on the system.
It experiences only forces originating from within.
None of the above
QUESTION 3
Which of the following statements about cars indicates that they are an open system?
OPTIONS
Friction is present between different parts of the engine.
The car burns gasoline and produces exhaust.
The engine heats up as the car is driven.
The faster the car is driven, the faster its tires turn.
QUESTION 4
What is the most common use of closed systems?
OPTIONS
To minimize environmental damage
To create more efficient systems
To simplify system analysis
To predict system structure and behavior
QUESTION 5
Which of the following questions is important for deciding whether a system is open or closed?
OPTIONS
Does the system exchange matter with its surroundings?
Is the system composed of multiple parts?
Does the system contain more than one state of matter?
Is the system natural or man-made?