WILL GIVE BRAINLIST brief history of coal. the inventors of who discovered coal and when was it first used.

Coal was one of man's earliest sources of heat and light. The Chinese were known to have used it more than 3,000 years ago. The first recorded discovery of coal in this country was by French explorers on the Illinois River in 1679, and the earliest recorded commercial mining occurred near Richmond, Virginia, in 1748

Explanation:

The coefficient of kinetic friction does not depend on speed. The equation expressing the relationship between kinetic-friction force and normal force is fk=uk·Fn. We can see that the coefficient of kinetic friction, uk, is proportional to the magnitude of normal force, Fn.

The coefficient of kinetic friction should depend on the type of surface you're working with.