) 650. J is the same amount of energy as _ A) 155 cal B) 2720 cal C) 650. cal D) 1550 cal E) 2.72 cal
The Correct Answer and Explanation is:
The correct answer is A) 155 cal.
To understand why, let’s first look at the relationship between joules and calories. The conversion factor between joules (J) and calories (cal) is:1 J=0.239 cal1 \, \text{J} = 0.239 \, \text{cal}1J=0.239cal
This means that to convert joules to calories, you multiply the amount of energy in joules by 0.239.
Now, let’s convert 650 joules to calories:650 J×0.239 cal/J=155.35 cal650 \, \text{J} \times 0.239 \, \text{cal/J} = 155.35 \, \text{cal}650J×0.239cal/J=155.35cal
This rounds to 155 calories, which is choice A.
Why this conversion matters:
Joules and calories are both units of energy, but they are used in different contexts. Joules are the SI (International System of Units) standard for measuring energy, while calories are commonly used in the field of nutrition to express the energy content of foods. Understanding the conversion between these units can be useful in many scientific applications, including biochemistry and physics, where energy transfer, chemical reactions, and metabolic processes are studied.
In nutrition, for example, energy content in foods is typically listed in calories. If you have a device like a thermometer or a heat source measured in joules and you want to know how much energy it corresponds to in calories (e.g., for food energy purposes), this conversion is crucial.
Further Example:
To see the impact of the conversion factor, consider converting larger amounts. If you had 1000 J of energy, that would be:1000 J×0.239 cal/J=239 cal1000 \, \text{J} \times 0.239 \, \text{cal/J} = 239 \, \text{cal}1000J×0.239cal/J=239cal
So, the conversion factor of 0.239 is consistently applied to switch between the two units.
