ANS:C - kinetic energy

At the boiling point of a liquid, the molecules in the liquid are in equilibrium with the molecules in its vapor phase. At this equilibrium, the average kinetic energy of the molecules in the liquid phase is equal to the average kinetic energy of the molecules in the vapor phase. Therefore, the correct answer is: Kinetic energy Equal average kinetic energies ensure that molecules are leaving the liquid (as vapor) at the same rate at which they are returning to the liquid (from the vapor), maintaining a dynamic equilibrium. This equilibrium is a result of the balance between the intermolecular forces holding the liquid together and the energy required for molecules to overcome these forces and escape into the vapor phase. Kinetic energy is a fundamental concept in physics that relates to the energy an object possesses due to its motion. It's a type of energy associated with the motion of an object, whether it's translational motion (movement from one place to another), rotational motion (spinning or rotating), or vibrational motion (oscillation). Here's a breakdown of key points about kinetic energy:

1. Definition: Kinetic energy is defined as the energy an object possesses due to its motion. Mathematically, it's expressed as: 𝐾.𝐸.=12𝑚𝑣2K.E.=21​mv2 where:
   • 𝐾.𝐸.K.E. is the kinetic energy,
   • 𝑚m is the mass of the object, and
   • 𝑣v is the velocity (speed) of the object.
   This equation shows that the kinetic energy of an object increases with both its mass and the square of its velocity. Therefore, an object with a greater mass or a higher velocity will have a higher kinetic energy.
2. Units: The SI unit of kinetic energy is the joule (J), which is equivalent to 𝑘𝑔⋅𝑚2/𝑠2kg⋅m2/s2. However, other units such as the calorie (cal) or the electronvolt (eV) are also used depending on the context.
3. Relation to Work: Kinetic energy is closely related to work, as both involve the transfer or conversion of energy. When work is done on an object, it can change its kinetic energy, either increasing it (if work is done to increase the object's speed) or decreasing it (if work is done to slow down or stop the object).
4. Conservation of Energy: According to the principle of conservation of energy, the total mechanical energy (which includes both kinetic energy and potential energy) of a system remains constant if only conservative forces are acting on it. This means that kinetic energy can be transferred from one object to another or transformed into other forms of energy, but the total amount of kinetic energy within a closed system remains constant.
5. Role in Physics: Kinetic energy plays a crucial role in various branches of physics, including mechanics, thermodynamics, and particle physics. It's used to analyze the motion of objects, determine the work done by forces, calculate the energy of particles in collisions, and understand phenomena such as heat transfer and phase changes.