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What defines a system?
What defines a system?
A system, as it is defined in physics or chemistry, is nothing more than a collection of objects (or smaller systems) that can be identified. Usually, the word system refers to a collection that makes thinking about a problem more convenient. The surrounding is everything else that is not the system defined. For example, if the system being studied is a house, the surrounding would be everything else that is not the house (other houses, the neighbourhood, the general environment around the house, etc.). Systems can be described in three different ways[1]:
This is an isolated system. The system is the thermos and the surrounding is the kitchen.[2]
This is a closed system. The system is the pan/lid and the surrounding is the kitchen.
This is an open system. The system is the pan and the surrounding is the kitchen.
Often, the most convenient system is an isolated system, one where outside influences can be ignored (either because they cancel out or because outside influences are negligible). For example, two balls rolling across a smooth surface to strike each other can be considered an isolated system, while two balls rolling across a gravel path or thick carpet are influenced by friction originating from outside the system and therefore are not an isolated system.
Defining Systems and Identify Energies
Defining Systems and Identify Energies
Create a sketch of the system. Include the following:
Dotted line to define the system.
Labels of objects within the system (annotate).
Identify important objects outside the system.
Describe if your system is Isolated, Closed or Open.
Show what you did or the procedure you followed at the station from beginning to end. Include an accurate description of the items involved as well as actions performed.
Describe what you saw or observed during this event. DO NOT CONFUSE what you saw/observed with what you think is happening.
Describe what specific changes you observed during this event, from beginning to end.
Based on your observations and prior knowledge, what conclusions can you draw concerning changes in the system during the event?
Based on your observations, identify the various types of energy within the system for 3-5 different times in your system.
A. Cart on Floor
A. Cart on Floor
Directions:
Using the switch on the bottom of the buggy, turn the buggy on.
Place the buggy on the floor.
Make observations.
Turn the buggy off.
B. Launched Ball
B. Launched Ball
Push the ball down to the first position (1-click).
Pull the string to release the ball.
Replace the ball into the launcher.
C. Bouncing Balls
C. Bouncing Balls
Drop the two balls from the same height.
Compare the motion of the two balls.
D. Pull-back Car
D. Pull-back Car
Pull the car back.
Release.
Describe the motion of the car.
E. Tuning Fork
E. Tuning Fork
Grasp the single end of the tuning fork. Tap the open end of the tuning fork with the rubber mallet or against the palm of your hand. Please, do not hit the tuning fork on the table.
Make observations.
Repeat striking the tuning fork with the mallet or palm, and this time place the open end of the fork so that it just touches the surface of the water in the shallow dish.
Make observations.
F. Cart on a Ramp
F. Cart on a Ramp
Push the cart up the ramp.
Describe the motion of the cart after it leaves your hand until it reaches the bottom of the ramp.
G. Mass on a Spring
G. Mass on a Spring
Mark where the spring is hanging in equilibrium (at rest).
Lift the spring gently and release.
Describe the motion of the mass and the various types of energy involved.
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