By burning 1 g of coal, the energy produced is 2 kcal. Then for 1 kWh, the quantity of coal required will be nearly:
Correct answer: C. 2/5 kg
- A. 9 kg
- B. 4/5 kg
- C. 2/5 kg
- D. 3/14 kg
Explanation
To find out how much coal is needed for 1 kWh, we start by converting kWh to kcal. Since 1 kWh is equivalent to 860 kcal, we can calculate the amount of coal needed. Given that burning 1 g of coal yields 2 kcal, we can compute:Energy from 1 g of coal: 2 kcalEnergy needed: 860 kcalCoal needed = (860 kcal) / (2 kcal/g) = 430 g = 0.43 kg.Since the question asks for the nearest option in kilograms, 0.43 kg is approximately equal to 2/5 kg. Therefore, Option C is correct.Options A, B, and D are incorrect because they either overestimate or underestimate the required amount of coal based on the data provided in the question.
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Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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