Ans: Motion can be classified as: a) When a particle moves along a straight line, or a path is said to undergo one-dimensional motion. For example, the motion of a train along a straight line, freely falling body under gravity, etc. b) A particle moving in a plane is said to undergo a two-dimensional motion—for example, the motion of a shell fired by a gun, carrom board coins, etc. c) A particle moving in space is said to undergo three-dimensional motion. For example, the motion of a kite in the sky, the motion of an aeroplane, etc.