Question

Which of the following is an example of the first law of thermodynamics ?

• A. The specific heat of an object explains how easily it changes temperatures.
• B. While melting, an ice cube remains at the same temperature.
• C. When a refrigerator is unplugged, everything inside of it returns to room temperature after some time.
• D. After falling down the hill, a ball's kinetic energy plus heat energy equals the initial potential energy.

Answer 1

The correct option is D After falling down the hill, a ball's kinetic energy plus heat energy equals the initial potential energy.

Explanation:
The first law of thermodynamics is another wording of the law of conservation of energy. Effectively it states that energy cannot be created or destroyed, but it can change forms.
This means that, in the given situation of the ball rolling down the hill, the total initial energy equals the final kinetic energy plus heat.
The zeroth law of thermodynamics states that if a system is in equilibrium with two other systems, then the two other systems are in equilibrium with each other.
The second law of thermodynamics states the entropy of a closed system will always increase.
The third law of thermodynamics states that absolute zero is the temperature at which entropy is zero.