ANS:A - surface energy created by crushing to the energy absorbed by the solid.

Crushing efficiency is the ratio of the energy absorbed by the solid to that fed to the machine.

Explanation:

• Crushing Efficiency: This term refers to how effectively a crushing machine converts input energy into desired particle size reduction. It is quantified by the ratio of the actual energy absorbed by the solid material being crushed to the energy input supplied to the machine.
• Options Analysis:
  • Surface energy created by crushing to the energy absorbed by the solid: This ratio does not define crushing efficiency but rather relates to how energy is transformed during the crushing process.
  • Energy absorbed by the solid to that fed to the machine: This correctly represents crushing efficiency, as it indicates how much of the input energy is utilized effectively for crushing the solid material.
  • Energy fed to the machine to the surface energy created by crushing: This ratio does not define crushing efficiency but rather compares input energy to surface energy generated.
  • Energy absorbed by the solid to the surface energy created by crushing: This ratio also does not define crushing efficiency but rather relates to the transformation of energy during crushing.

Therefore, crushing efficiency is correctly defined as the ratio of the energy absorbed by the solid material being crushed to the energy input supplied to the crushing machine. This ratio helps in assessing how effectively the machine converts input energy into the desired particle size reduction.