CBSE Physics Class IX (9th) Motion

Motion: When an object change its position with respect to time and surrounding then the object is said to be in motion.

Example: Moving car, bus etc since they change their position with respect to time.

Rest: When an object does not change its position with respect to time and surrounding then the object is said to in rest.

Example: House, tree, mountain etc since they do not change their position with respect to time.

Motion along a straight line:

When an object moves on a straight line then the motion of the object is called rectilinear motion.

Example: Moving car along a straight road.

Displacement and Distance:

Displacement: The change of position of a moving body in a particular direction is called its displacement.

The magnitude of the displacement is the linear distance between the initial position and final position of the body.

Since displacement has both direction and magnitude, it is a vector quantity.

C.G.S and S.I unit of displacement are centimetre(cm) and metre(m) respectively.

Distance: The length covered by a moving object at a given time is called distance.

Distance has only magnitude, so it is scalar quantity.

C.G.S and S.I unit of distance are centimetre and metre respectively.

Difference between displacement and distance:

Displacement	Distance
1. The change of position of a moving body in a particular direction is called its displacement. 2. It is a vector quantity 3. The displacement of a moving object may be zero.	1. The length covered by a moving object at a given time is called distance. 2. It is a scalar quantity. 3. The covered distance of a moving object never be zero.

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