A system's internal energy is given by the heat added to the system less the work done by the system
1) 12 units of movement energy cannot by produced from 10 units of elastic energy because the additional 2 units of energy cannot be created in the closed system of the rubber band
2) Part A; The percentage efficiency = 70%
Part B; The remaining 3 units is transformed into heat and sound energy
3) The by-products of the energy transformation for a car are;
The reason for the above outcomes is as follows:
1) The first law of thermodynamics known as the law of conservation of energy states that the sum of energy within an closed or isolated system is constant and it is conserved as time progresses
Mathematically, the law can be expressed as follows;
K₁ + U₁ = K₂ + U₂
Where;
K₁ and U₁ = Initial kinetic and potential energy respectively
K₂ and U₂ = Final kinetic and potential energy respectively
The energy stored in the rubber band is given as 10 units of elastic energy. If the rubber band is taken as being in a closed system, then no additional energy is added, and we have;
U₁ = 10 units and K₁ = 0, which gives;
K₁ + U₁ = 10 units
According to the law of conservation of energy, we get;
10 units = K₁ + U₁ = K₂ + U₂
Therefore, the sum of the final kinetic and potential energy is 10 units and the energy can only be transferred from kinetic to potential (internal) energy, such that the maximum kinetic, movement, energy obtainable is 10 units and 12 units of movement energy cannot be produced
2) The given parameter:
Initial amount of elastic energy = 10 units
The amount of movement energy produced = 7 units
[tex]Efficiency = \mathbf{\dfrac{Useful \ energy \ produced}{Total \ energy \ stored} \times 100}[/tex]
[tex]\mathbf{Efficiency \ of \ the \ rubber \ band, \, \eta }= \dfrac{Movement \ energy \ produced}{Elastic \ energy \ stored} \times 100[/tex]
Therefore;
[tex]\mathbf{\eta = \dfrac{7}{10} \times 100} = 70 \%[/tex]
The percentage efficiency of the rubber band, η = 70%
Part B
The remaining 3 units of energy is transformed into other energy forms including heat and sound energy
3) A by-product is a secondary product, produced in addition to a main or primary product.
In the energy transformations of a car, the main product of the energy transformation is the movement energy of the car
The by-product of the energy transformation in a car includes;
Heat energy; The temperature of the engine of the car rises
Sound energy; The engine sound
Chemical energy; The formation of new chemicals during the combustion process
Learn more about conservation of energy here:
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