Final answer:
The machine with an efficiency of 20% and an energy input of 200 joules/second will generate 24 kJ of useful energy in 10 minutes. You find this by first calculating the total energy in joules over the 10 minutes and then applying the efficiency as a percentage to find the useful energy output. The correct answer is option B.
Step-by-step explanation:
The question deals with the concept of energy efficiency in physics. To find the useful energy generated by the machine, you need to multiply the energy input per second by the efficiency of the machine, and then multiply by the total number of seconds in 10 minutes.
The machine's efficiency is 20%, which means that only 20% of the energy input is converted into useful energy. The energy input is 200 joules/second. To find the energy per minute, you multiply 200 joules/second by 60 seconds, which gives you 12,000 joules/minute. Since there are 10 minutes, we then multiply 12,000 joules/minute by 10, resulting in 120,000 joules over the whole period.
To get the useful energy, we take 20% of 120,000 joules:
- Useful energy = Energy input × Efficiency
- Useful energy = 120,000 J × 0.20
- Useful energy = 24,000 J or 24 kJ (since 1 kJ = 1,000 J)
The machine will generate 24 kJ of useful energy in 10 minutes. So, the correct answer is B. 24 kJ.