Fundamental Knowledge of Science Flashcards

In the context of mine explosions, what is the Lower Explosive Limit (LEL) of methane in air?

Answer: 5%

Methane's LEL is 5% by volume in air; below this concentration the mixture is too lean to ignite.

Which type of radiation can be stopped by a sheet of paper and poses the least penetrating hazard in mining?

Answer: Alpha radiation

Alpha particles have very low penetrating power and are stopped by a sheet of paper or a few centimeters of air, though they are hazardous if inhaled.

What chemical property makes hydrogen sulfide (H₂S) particularly insidious as a mine hazard?

Answer: High concentrations paralyze the olfactory nerve, removing the warning smell

At high concentrations H₂S rapidly paralyzes the olfactory nerve so workers can no longer smell it, eliminating the natural warning of its rotten-egg odor.

Which Newton's law is most directly applied when calculating the force required to move a loaded mine cart?

Answer: Newton's Second Law (F = ma)

Newton's Second Law (F = ma) directly relates the net force needed to accelerate a mass, making it the basis for calculating haulage forces.

When coal dust is suspended in mine air, it becomes explosive primarily because:

Answer: Suspended particles dramatically increase the surface area available for rapid oxidation

Suspending dust creates an enormous surface area-to-mass ratio, allowing very rapid oxidation (combustion) when an ignition source is present.

pH is defined as the negative logarithm of which ion concentration?

Answer: Hydrogen ion (H⁺) concentration

pH = −log[H⁺]; lower pH means higher hydrogen ion concentration and stronger acidity.

In electrical circuits used in mines, Ohm's Law states:

Answer: Voltage equals current multiplied by resistance (V = IR)

Ohm's Law: V = IR, where voltage (V) equals current (I) in amperes times resistance (R) in ohms.