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ジ
CHAPTER 8
MOTION
CHAPTER^ NOTES
FOR^ CLASS^ 9TH
DATE:
수
MOTION
"The change in position^ with^ time."
1. INTRODUCTION
Motion is a change in position
of an object with respect to time.
It is a relative term.
The object may be moving
or at rest.
2. TYPES OF MOTION
FOR
CLASS^ 9TH
NOTES
Rectilinear Motion - Motion in a
straight line.
Curvilinear Motion - Motion
along a curved path.
Circular Motion - Motion along
a circular path.
Uniform
speed
- KEY TERMS
Distance - Total length of the actual path traveled.
Displacement - Shortest distance from initial to
final position in a given direction.
A
Speed - Distance traveled per unit time.
Velocity - Displacement per unit time in a
given direction.
DISPLACEMENT VS DISTANCE
B
Velocity is
constant.
Direction is
changing.
Distance
= Displacement
FORMULAS
4. EQUATIONS OF MOTION
(for uniform acceleration)
5. GRAPHICAL REPRESENTATION Av
a=
a) Position - Time Graph^ t
1 v= u+ at u = Initial velocity
Position
②s= ut+at²
v = Final velocity Slope = Velocity
a = Acceleration
in the direction
of acceleration.
Time
3 v² = u² + 2as t = Time
b) Velocity - Time Graph
u+ v
4 s=^ t
s = Displacement
Velocity
Slope = Acceleration
Stay
Curious!
- POINTS TO REMEMBER
★Motion is relative.
★More than one frame of reference.
★Rest is also a type of motion (zero velocity).
★The direction of velocity may change even if speed is constant.
Time
Practice
makes
Perfect!
0
(InitialA Position)
Line^ in^ Motion
FAST REVISION: MOTION
(Final^ B Position)
Distance Displacement = Length = AB of line (AB)
Speed Velocity = = Distance Displacement/Time / Time
MOTION
FAST^ REVISION
Motion:-^ position^ of^ object^ changes with
time.
eg^ moving^ car,^ flyingbird
Rest:^ position^ of^ object^ does^ not change
with time.
a person is sitting
MOTION^ IS^ RELATIVE
Girk
isat
Rest.
SCHOOL BUS
Girl is
in Motion
Distance = 2TR = 2x22x14=^ 88m 7
Displacement^ =^0
be greater^ than
Distance
Distance
Length of actual total path
covered
Has only magnitude
Scalar quantity
Can never be negative
Depends on the path followed
Displacement Shortest^ path^ from^ initial position to final position. Has magnitude^ &^ direction
Vector quantity
Can be positive, negative, zero
Depends^ only^ on^ initial^ and^ final
Km
Distance^ :-^ Length.actual path covered.
Displacement:-^ shortest^ path^ from
starting^ (initial)^ point^ to^ ending
(final)^ point,^ along^ the direction.
Distance
Displacement
ABCB
A^5 m B^10 m^ C
Distance^ =^ 5+10+10^ =25m
Displacement^ =^ 5m
Displacement^ can
be^ negative
by object.^ position,^ not^ on^ path^ followed.
Speed-^ Distance^ covered^ perunit
time.
Distance
(speed^ =
time
S-I unit=^ m/s anotherunit=^ km/h
Velocity:-^ Displacement
per unittime.
Velocity^ Displacament Time
srunit=^ m/s
another^ unit=^ km/h
speed^ with^ direction^ is^ velocity
10 m, t= 2s
speed=^ Dist^ =^10 =^ 5m/s
time^2
Velocity=^ Y=^ Disp^10 =+5m/s
time^2
Disp-m Disp=+hm
•Distance^ is
Always
Positive
•Dis^ placement^ canbe zero^ even^ after
bocly^ has^ moved
Radius=^ 14m
After^ Lcomplete Revolition
10 m, t=2s
speed=^ Dist^ =
10 =^ 5m/s
time^2
Velocity^ =^ Disp^ =-10^ =^ -5m/s time 2
4m t= 2s
t= 6s
Equations of^ Motion:-
When^ object^ travels^ in^ a^ straight line
with UNIFORM^ (SAME)^ ACCELERATION
•V= Utat
S= ut+2at²
V²=4²+ 29s
V=^ finalvelocity^ (m/s)
u=^ initial^ Velocity^ (m/s)
a=^ acceleration(m/s)
t= time^ (s)
s= displacement^ or distance^ (m)
A bus starting^ from^ rest^ moves^ with^ a^ uniform^ acceleration^ of
0.1 m s-2 for 2 minutes. Find -
(a) the speed acquired, V=?
(b) the distance^ travelled(s)^ starts^ fromrest^ 24=0,
a=^ 0.1^ m/s
t=2x60=120s
Uniform^ circular
Motion:-
a) circular Motion^ with^ same^ speed speed = constant^ uniform^ speed
2 velocity=> changes?
Magnitude of velocity-same; Direction of velocity- changes
lomls
C
v = 10 m/s
(3)^ Hcceleration^ is^ Not^ Zero.
speed
V= 2AR
T
TTime^ for complete Revolution
*A^ satelite^ revoluing around^ earth^ in circular
orbit^ with^ constant(same) speed.
A^ cyelist^ on^ b Cicular^ track at constant speed.
