One calorie of heat energy is equivalent to approximately ______ joules of mechanical energy.

4.2

The correct answer is option 4. 4.2.

Let us break down the explanation:

A calorie is a unit of energy commonly used in the field of nutrition and thermodynamics. It is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius.

On the other hand, a joule is the standard unit of energy in the International System of Units (SI). It is defined as the amount of work done when a force of one newton is applied over a distance of one meter.

The conversion factor between calories and joules is approximately 4.2 joules per calorie. This means that one calorie is equivalent to approximately 4.2 joules of mechanical energy.

So, to convert from calories to joules, you would multiply the number of calories by 4.2. Conversely, to convert from joules to calories, you would divide the number of joules by 4.2.

This conversion factor is useful when comparing energy values expressed in different units or when performing calculations involving energy transfer between mechanical and thermal forms.