Bicycle device. What are the names of these two? (with pictures. )

The first one is called flywheel, and the second one is called brake line (car brake).

The second type is not completely called brake pad, because its structure is different from that of brake pad. The landlord can look at the brake device of car wheels, called brake pads, and bicycles have similar structures, generally called disc brakes. But the one in your picture can only be called a brake. . . Or a V-type brake (corresponding to a disc brake)

As for the first one, it is the principle of gear without increasing or decreasing friction. I don't know how old the landlord is. I can learn pulley in junior high school. Similarly, bicycles use different transmission ratios of front and rear axles to achieve results.