question_answer 1)

Which of the following examples represent periodic motion? (a) A swimmer completing one (return) trip from one bank of a river to other bank. (b) A freely suspended bar magnet displaced from its N-S direction and released, (c) A hydrogen molecule rotating about its centre of mass. (d) An arrow released from a bow.

Answer:

(a) It is not a periodic motion. Though the motion of a swimmer is to and fro but will not have a definite period. (b) It is a periodic motion because a freely suspended magnet if once displaced from N-S direction and let go, it oscillates about this position. Hence it is simple harmonic motion also. (c) It is also a periodic motion. (d) It is not a periodic motion.