# MOTIONS IN ONE, TWO AND THREE DIMENSIONS (TYPE OF MOTION)

## Motion of Class 9

As position of the object may change with time due to change in one or two or all the three coordinates, so we have classified motion as follows:

## MOTION IN ONE DIMENSION:

If only one of the three co-ordinates specifying the position of object changes w.r.t. time. In such a case the object moves along a straight line and the motion therefore is also known as rectilinear or linear motion.

Ex.

• Motion of train along straight railway track.
• An object falling freely under gravity.
• When a particle moves from P1 to P2 along a straight line path only the x-co-ordinate changes.

### MOTION IN TWO DIMENSION:

If two of the three co-ordinates specifying the position of object changes w.r.t. time, then the motion of object is called two dimensional. In such a motion the object moves in a plane.

Ex.

• Motion of queen on carom board.
•  An insect crawling on the floor of the room.
• Motion of object in horizontal and vertical circles etc.
• Motion of planets around the sun.
• A car moving along a zigzag path on a level road.

### MOTION IS THREE DIMENSION:

If all the three co-ordinates specifying the position of object changes w.r.t. time, then the motion of object is called 3-D. In such a motion the object moves in a space.

Ex.

• A bird flying in the sky (also kite).
• Random motion of gas molecules.
• Motion of an aeroplane in space.