Which of the following example 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.

Which of the following example represent periodic motion (a) A swimmer

1.	Which of the following example 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» Solution :(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 it 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.