An object in uniform circular motion must be changing its speed in order move in a circular path

No, that statement is false.

In uniform circular motion, the direction is constantly changing, but the speed is constant.

the word that best describes martin luther king jr.'s tone in the video is dignified

martin luther king, jr. was a social activist and baptist minister who played a key role in the american civil rights movement from the mid-1950s until his assassination in 1968. the video shows his manner and attitude having or showing a composed or serious manner that is worthy of respect so dignified is the correct answer