Question

The thermal motion means
A. Motion due to heat engine
B. Disorderly motion of the body as a whole
C. Motion of the body that generates heat
D. Random motions of molecules

Answer 1

Hint: The thermal motion is the pointless motion of the molecules of the body. This information is key to solve this problem.

Complete step by step solution:
Thermal motion is the random motion of the micro particles such as atoms, molecules etc.
It is different from ordinary mechanical motion because the body moves in all manners. It is a different kind of motion of the matter.
The thermal energy is measured by the temperature. The energy contained in the small amount of motions of the object’s molecules can be broken up into the combination of the microscopic kinetic energy and the potential energy. When a substance heats up the rise in the temperature makes these particles move faster and bump into each other. The thermal energy is the energy that comes from the heated up substance. The hotter the substance, the more its particles move, and the higher its thermal energy.
When a system absorbs heat from the surroundings or when we supply thermal energy to the system, the internal energy of the system increases. The heat absorbed increases the kinetic energy of the molecules causing them to move randomly.
Random motions of the molecules.

So, the correct answer is “Option D”.

Note: Temperature measures the average kinetic energy of the particles in a substance. Thermal energy measures the total kinetic energy of the particles in a substance. The greater the motion of the particles, the higher the substance's temperature and thermal energy.