motion of which of the following is not periodic

a).beating of a drum.

b).revolution of moon around the earth

c).rotation of the earth around its axis.

d). movement of a pendulum.

 Hi,

b). and c). are not periodic motion. These are circular motion.

Periodic motion:Motion that repeat itself after some time, is called Periodic motion.

Eg. (1)pendulum of a clock

  (2) child in a swing

 

Circular motion:In circular motion an object moves such that its distance from a fixed point remains the same.

Eg. (1) fan

  (2)b). & c).

Motion in a straight line, is called Rectilinear motion.

Eg. (1)an army parade

  (2) cars and buses on a highway...

Hope it helps....