CBSE Class 9 Answered

In physics, circular motion is rotation along a circle: a circular path or a circular orbit. It can be uniform, that is, with constant angular rate of rotation, or non-uniform, that is, with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves circular motion of its parts. The equations describing circular motion of an object do not take size or geometry into account, rather, the motion of a point mass in a plane is assumed. In practice, the center of mass of a body can be considered to undergo circular motion.

Examples of circular motion include: an artificial satellite orbiting the Earth in geosynchronous orbit, a stone which is tied to a rope and is being swung in circles (cf. hammer throw), a racecar turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field, and a gear turning inside a mechanism.

Linear motion is motion along a straight line, and can therefore be described mathematically using only one spatial dimension. The linear motion can be of two types, Uniform Linear motion, with constant velocity or zero acceleration, Non Uniform Linear motion, with variable velocity or non-zero acceleration. The motion of a particle (a point-like object) along a line can be described by its position x, which varies with t (time). Linear motion is also called as rectilinear motion.[1]

Linear motion is the most basic of all the motions.
Since Linear motion is a motion in a single dimension, distance traveled by an object is same as displacement.
An example of linear motion is that of a ball thrown straight up and falling back straight down.