Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately ?

The correct answer is:

C. Bond's law

Explanation:
When dealing with intermediate particle size reduction, especially in the range of 100 mesh to 325 mesh (like -200 mesh), Bond's law provides the most accurate estimation of the energy required.

Here's a quick comparison of the laws:

Rittinger’s Law: Best for fine grinding (very small particles); assumes energy is proportional to new surface area created.

Kick’s Law: Best for coarse size reduction; assumes energy is proportional to volume reduction.

Bond’s Law: Most accurate for intermediate size reduction, such as coal to -200 mesh; it uses a work index and considers the square root of particle sizes.

So, for coal ground to -200 mesh in a ball mill, Bond's law is the most suitable.
✅ Correct Answer: C. Bond's law

200 mesh is very small and when the particle diameter is very less Rittinger's law (n=2) is useful