Assuming 50% efficiency, 150 kcals of chemical energy would result in __ of kinetic energy.
The correct answer and explanation is:
Correct Answer: 75 kcals of kinetic energy
Explanation (300 words):
Energy efficiency refers to the proportion of input energy that is converted into useful output energy. In this case, the input energy is chemical energy, and the useful output energy is kinetic energy (the energy of motion). The remaining energy is typically lost as heat or other unusable forms.
If a system has 50% efficiency, it means that only half of the input energy is successfully converted into the desired form—here, kinetic energy.
Step-by-step Calculation:
- Given:
- Input chemical energy = 150 kilocalories (kcals)
- Efficiency = 50% or 0.50
- Calculate output kinetic energy: Kinetic Energy Output=Input Energy×Efficiency\text{Kinetic Energy Output} = \text{Input Energy} \times \text{Efficiency} Kinetic Energy Output=150 kcals×0.50=75 kcals\text{Kinetic Energy Output} = 150 \, \text{kcals} \times 0.50 = 75 \, \text{kcals}
So, 75 kilocalories of kinetic energy will result from 150 kcals of chemical energy at 50% efficiency.
Why This Matters:
Understanding energy efficiency is essential in fields such as biology, physics, and engineering. For example, in the human body, chemical energy from food is converted into kinetic energy during physical activity. However, the human body isn’t 100% efficient—much of the energy is lost as heat. Machines also have varying efficiencies depending on design and friction losses.
This principle helps:
- Design better engines and machines.
- Understand how organisms use energy.
- Improve energy conservation in systems.
A 50% efficiency is relatively high for biological systems but is used here for simplicity in calculations. In reality, human muscle efficiency is closer to 25–30%, meaning even more energy is lost as heat.