The rotation of the earth about its axis is:

(a) periodic motion

(b) simple harmonic motion

(c) periodic but not simple harmonic motion

(d) non-periodic motion

Choose the correct alternatives:

1. (a, b, d)

2. (a, c)

3. (b, d)

4. (c, d)

(1, 3) Hint: In SHM, the body does to and fro motion.

The rotation of the earth about its axis is periodic because it repeats after a regular interval of time.

The rotation of the earth is obviously not a to and fro type of motion about a fixed point, hence its motion is not SHM.