1. · Explain the origin of coal and name its various varieties. 2. Define the following:
(i) Coal gas
(ii) Coal tar
(iii) Coke

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system.It is produced when coal is heated strongly in the absence of air. ... Facilities where the gas was produced were often known as a manufactured gas plant (MGP) or a gasworks.

Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoriasis and seborrheic dermatitis (dandruff). It may be used in combination with ultraviolet light therapy.

: a bituminous coal suitable for making into coke.

the speed increase from w to x due to increased gravity force

the speed decreases from x to y due to decrease in gravity