Motion Class 9 Notes Science Chapter 8

Stationary
Object:-The object
which remains Fixed at a place is called Stationary object.

E.g:-Trees, a house, a school, a factory

Moving
Object:- The object
which can move from one place to another is called moving object.

E.g:- a man moves when he walks along a
road, a bird moves when it flies in   the
sky etc….

Note:- A common characterstics of all the
moving bodies is that they change their position with time.

Reference
Point:- A body is
said to be in motion (or moving) when its position changes contiously with
respect to a stationay object taken as reference point.   

Note:-If a body moves fairly fast, then
its movement(or motion) can be observed easily. But if a body moves very
slowly, the it become difficult to observe its movement immediately.

               E.g:- A wrist watch has
three hands:- a second hand, a minute hand and an hour hand, which moves round
and round on the dial of the watch. Now, the seconds’ hand of watch moves quite
fast, so we can observe the movement of the second hand of watch very easily.
But the minutes hand and an hour hand of a watch moves quite slowly, so their
movement cannot be observed easily.

Motion:- The body is said to be in motion
when its position changes continuously with respect to time.

Note:- Physical quantity:- The quantity
which can be measured or quantities of Physics

E.g. The quantity like distance,
displacement, etc. are known as physical quantity.

Scalar
Quantity:- A
physical quantity having only magnitude( or size) is known as a scalar
quantity.

E.g:- Distance, speed, mass, length, time

Vector
Quantity:- A
physical quantity having magnitude as well as direction is called vector
quantity.

E.g:- Displacement, velocity,
acceleration, force, moventum, torque, Angular movementum

Distance
Travelled and Displacement

Distance(‘D’):- The distance travelled by a body is
the actual length of the path covered by a moving body irrespective of the
direction in which the body travels.

E.g:- In this case, the actual length of
the path covered by the man is 5km+3km=8km, so the distance travelled by the
man is 8km.                                      

Note:- If we a round trip and reach back at the starting point then, though we have travelled some distance, our final displacement will be zero. This is because the straight line distance between the initial and final position will be zero.

Note:- Whenever a body travels along a zig-zag path, the final displacement is obtained by joining the starting point and finishing point of the body by straight line.

Uniform Motion And Non-Uniform Motion