Question

Grindability of a material does not depend upon its

• A. size
• B. toughness
• C. elasticity
• D. hardness

Hint:

Think of grindability as a material constant, similar to density or thermal conductivity. These are intrinsic properties. Size, mass, and volume are extrinsic properties that describe a specific sample, not the material in general.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Grindability is an intrinsic property of a material that describes its resistance to grinding or crushing. A material with high grindability is easy to grind, while one with low grindability is difficult to grind. This property depends on the material's mechanical characteristics that influence how it fractures under stress.

Step 2: Detailed Explanation:
Let's analyze the factors listed: -

Hardness: Hardness is a measure of a material's resistance to localized plastic deformation such as scratching or indentation. A harder material is generally more difficult to grind, so grindability depends on hardness. -

Toughness: Toughness is a material's ability to absorb energy and plastically deform without fracturing. A tough material can absorb a lot of strain energy before it breaks, making it difficult to grind. Therefore, grindability depends on toughness. -

Elasticity: Elasticity is the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force is removed. While related to how a material behaves under load, it's a fundamental mechanical property that influences fracture behavior. -

Size: The size of the particles is an extrinsic property, not an intrinsic one. While the energy required to grind a batch of material certainly depends on the initial and final particle sizes (according to Rittinger's, Kick's, or Bond's laws), the "grindability" itself is a material constant (like the Bond Work Index) that is determined experimentally and is considered a characteristic of the material, independent of the size of the specific sample being tested. For instance, the Hardgrove Grindability Index (HGI) is a standard test that measures the grindability of coal, and the result is a property of that type of coal, not of the specific particle size used in the test. Therefore, grindability is an inherent property of the material related to its structure and mechanical properties (like hardness, toughness, etc.), not its external dimensions like size.

Step 3: Final Answer:
The grindability of a material does not depend upon its size. This corresponds to option (A).