Unit B 3.1 Flashcards
What did scientists do that is the opposite of Rube Goldberg
They design efficient machines that exert the minimum possible effort to produce largest possible results.
How did they discover principles of heat behavior?
By trying to make machines more efficient
What are systems?
Is a set of interconnected parts; in work & energy transfers, the system is the object involved in a transfer
Also the boundaries for objects in a system
What’s an open system and give an example?
An open system exchanges both matter and energy with its surroundings
Ex: Earth is a system and the universe is the surroundings; earth is an open system because it can exchange both matter and energy with its surroundings
What’s a closed system and give an example?
A closed system exchanges only energy with it’s surroundings, but matter cannot get in or out
Ex. A closed can of soup, matter stays in and cant get out, but energy can come in and out
What’s an isolated system and give an example?
Neither matter nor energy can be exchanged
What is the difference between work and heat?
Work vs Heat:
- Work involves movement of matter from one place to another
- Heat is a transfer of thermal energy from one place to another
What are 2 ways the energy of a system can be increased?
Heat can be added to a system from surroundings
Work can be done on a system by surroundings
- Positive work because energy increases
What are 2 ways the energy of a system can be decreased?
Heat can flow out of a system to its surroundings
Work can be done by a system to its surroundings
- Negative work because energy of system decreases
What does the 1st law of thermodynamics state?
The total energy including heat in a system and its surroundings remains constant;
The amount of heat put into a system must equal the amount of mechanical energy plus heat lost by the system
What are 3 things that can happen when heat is added to a system?
- It transforms into an equal amount of some another form of energy
- Some of the energy goes into increasing the internal energy of the system thereby increasing the temperature as well
- Some of the energy is used to move parts or do work on a system which increases mechanical energy
What does the heat added to a system equal?
Mechanical energy + lost heat
What is a perfect/perpetual machine?
A perfect/perpetual machine is a machine that equals the input energy to output energy so meaning no energy is lost as heat
All the mechanical energy in a system must be conserved as mechanical energy during transformations to be perfect
So a 100% efficient system
What does the 2nd law of thermodynamic state?
Heat always flows naturally from a hot object to a cold one, but never naturally from a cold object to a hot one
Describes the direction of energy flow in natural processes
What is a heat engine?
When the heat in a heat engine flows from a high temp area to a low one, the heat can be converted into mechanical energy which can do work
- Only some of the input heat can be converted into mechanical energy
- Remaining heat is gone as exhaust heat
