What is a relative motion

The relative velocity is the velocity of an object or observer B in the rest frame of another object or observer A.

Taken from President John Kennedy's Rice Stadium Moon Speech (1962), the phrase that the President Kennedy repeated is “the first waves of” (“Those who came before us made certain that this country rode the first waves of the industrial revolutions, the first waves of modern invention, and the first wave of nuclear power, and this generation does not intend to founder in the backwash of the coming age of space.”). Kennedy repeated this phrase in his speech because he wanted to highlight the importance of leading the “coming age of space” as previous generations have done with previous important events, previous “first waves” (of industrial revolutions/of modern invention/of nuclear power). Then, he mentions that his generation would not fall behind. Kennedy also wanted to emphasize the unity as a nation, which shares a mission, by using the personal pronoun “we” in the following sentences (“We mean to be a part of it--we mean to lead it.”).