Final answer:
In rock music, a powerful beat in quadruple meter typically has strong accents on the second and fourth beats of each bar, known as the backbeat.
Step-by-step explanation:
Rock music is characterized by a strong rhythm, typically in a quadruple meter, which emphasizes certain beats in each bar. In the context of rock, this powerful beat often has strong accents on the second and fourth beats of each bar. The pattern of emphasis in rock, commonly known as the backbeat, contrasts with more evenly stressed beats in other musical forms or the stresses on the first and third beats as found in march music, for example. The impact of the backbeat is such that it can be clearly felt and heard, encouraging a physical response from the listener, often in the form of head nodding or foot tapping.