157315472 complete notes on 9th physics by asif rasheed

7/25/2019 157315472 Complete Notes on 9th Physics by Asif Rasheed

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XSAS

IDEAL SCIENCEACADEMY (CONTACT # 0344 -7

46 394 ) 9THCLASSPHYSICS NOTES

1) PHYSICALQUANTITIES &

MEASURMENTS

) !INEMATICS3) DYNAMICS

NOTES O" PHYSICS 9THCLASENLISH MEDIUM


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Ideal Science Academy

COMPLETE "IRST THREE

CHAPTER PRO$LEMS%SHORTAND LON QUESTIONS

IDEAL SCIENCE

ACADEMYASI" RASHEED $SHONS PHYSICS


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U' N 11 D*+* P,.'/.

A.The branch of science which deals with the study of matter andenergy and their mutual relationship is called Physics.

() 2'* 5*. ,* /,*. P,.'/.

A. (1 !echanics (2 "eat # Thermodynamics (3 Sound ($ %ight

(& 'lectromagnetism ( Atomic and !olecular Physics () *uclear Physics (+Plasma Physics (, Solid Physics

2, * .: ;,.'/.

-e study physics to under stand the laws of nature and how nature eects thehuman action.

3) D*+* P ,* ,* /,*. ./'*/*

A. (1 Astrophysics (2 0eophysics (3 iophysics

(7)2, .:'* ,* **


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Ideal Science Academydeals with the physical aspects of sound wa/es their production properties

nd applications.

L'>, (O;'/.4

It is the study of physical aspects of light its properties wor5ing and use ofptical instruments.

E*'.5

It is the study of the changes at rest and in motion their eects and theirelationships with magnetism.

A5'/ ;,.'/.

It is the study of the structure and properties of atom.

N:/*

A screw gauge is used to measure small lengths such as diameter of a wirehic5ness of a metal sheet etc.

The leastcountof micrometer screw gauge is


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Ideal Science AcademyP,.'/<


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Ideal Science Academy@nit of Area4 length : breadth@nit of length : unit of breadth!eter : meterm : m

4 m2

@nit of >olume4 length : breadth : height@nit of length : unit of breadth : unit of height!eter : meter : meterm : m : m4 m3

@nit of ?ensity4 !ass>olume

@nit of mass@nit of /olume4 2, '. ,* :5* .* :'. ' S.*5 I*'< (SI)A.@ There are se/en base units which are gi/en below*umber Physical uantity @nit Symbol1. %ength !eter (m2. !ass 9ilogram(5g3. Time Seconds (s

$. 'lectric current Ampere( A&. Temperature 9el/in( 9. Intensity of light Bandela(cd). Amount of substance(!ole mol

Q 2,** 5:


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Ideal Science AcademyQ1@7 2, '. 5* '. =*'* /.A.@

A /ernier calliper can be used to measure lengths accurately up to onetenth of a millimetre.

%east Bount;>ernier BonstantThe minimum length which can be measured accurately with the help of /erniscale or /ernier calipers is called least count.%east count of /ernier calliper is 1;1< mm or * 5*.:*. 5*//:*


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Ideal Science AcademyA. The stop watch is used to measure small inter/als of time. Its least couis about '+/ +>:*. ' 5*.:* ?:'Ans4 !ore is the number of signi=cant =gures when the measuring instrumentused has small /alue of its least count. The small /alue of least count the largeis the /alue of precision. For e:ample reading ta5en by screw gauge has moreprecision than reading ta5en by meter rod or /erneir scale.

CHAPTER 1 Physical 8uantities and measurement(Problems

P1@1) E;*.. ,* ;*+*.@S


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Page1ibratory !otion

2, '. ,* 5' :*K E*/:*


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Ideal Science AcademyFlight of butterCy is irregular motion. Therefore its motion is called randommotion.2, '. ;* 5' **


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Ideal Science AcademyD*+* U'5 S;**

If a body co/ers an e8ual distance in e8ual inter/al of time in a particula

direction the body is said to be uniform >elocity.

D*+* ='* =* ', /*' =*


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Ideal Science AcademyD*+* 'elocity;Total Time

G(>f 6 >it

D*+* =''< A//*='' ', :'5 .;**@ 2' ', /*' =*,% */, ,* >: ,* .5* '5*@ecause both ha/e same gra/itational acceleration.

11@ 2, ;* /,>* '='Acceleration (a will be replaced with gra/itational acceleration (g in alle8uations.

And distance (s will be changed in to height (h

D*./'* ,* 'J** ;*. 5' ' *'


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ii R M'7!otion is said to Lotatory when the obect rotates on its own a:i

':amples4 Lotatory motion of a planets on its a:is wheels of a /ehicles

spinning top ceiling fan etc.''') ' M' -

-hen a body mo/es to and fro about a point and repeats its motion the

its motion is called /ibratory motion. e.g. !otion of simple Pendulum motio

of tuning for5 A ruler. Place one inch of it on a des5 and the other 11 o

the des5. Flic5 the end o the des5 and watch it /ibrate.

2.1< "ow can a /ector 8uantity be represented graphicallyQ

Ans4 -hen a /ector is represented graphically its magnitude is represented bythe length of straight line and its direction is represented by the direction of th

arrow head . "ere is an e:ample 4

Q@11 2, =*/. ?:''*. / * * .:/*


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Ideal Science AcademyAns4 in our daily life /ectors 8uantities are completely e:plained only when

their direction are also considered 2.13 ?eri/e e8uation of motion for

uniformly accelerated rectilinear motionQ

Three e8uations of motion are three e8uations of motion under the action o

gra/ity are

>fG >i at >fG>igt

S G >it 1

2 at2 hG>it1

2 gt2

2aS G >f26 >i22gh G >f26 >i2

2.1$ 4 S5etch the /elocity time graph for the motion of the bodyQ

!otion 0raphs

" ody mo/ing at constant /elocity4

The graph of straight line parallel to the a:is shows that the body is mo/in

with constant /elocity

a
http://physics.tutorvista.com/motion/motion-graphs.htmlhttp://physics.tutorvista.com/motion/motion-graphs.html


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Page2ibe the initial /elocity of an obect and UaU the

acceleration produced in the body. The distance

tra/elled s in time t is gi/en by the area enclosed by

the /elocity7time graph for the time inter/al < to t.

?istance tra/elled S G area of the trapeDium

A?K

Total aera of KA?G area of rectangle AB?K area of VHAB

G K? : KA 1

2 (B : AB

-here KAG>I K?Gt BG?7B? ABGt ?G>f B?G>i

G t : >i1

2 (>f7 >i : t

G >i t 1

2 (>f7 >i : t

(/f G > i at I e8n of motion /f 7 /i G at


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S G >it 1

2 at : t

S G >it

1

2 at2

.

T,' E?:' M'%et U/iU be the initial /elocity of an obect and a be the acceleration produced i

the body. The distance tra/elledNsN in timeNtN is gi/en by the area enclosed by

the speed (/ 7 t graph.

SG area of the trapeDium KA?.

G (1

2) (KA ? : AB where KAG>i ?G >f ABGK?Gt

G (1

2) (>i >ft ....(1

ut we 5now that a G( >f7 >i)tKr t G (>f7 >ia

Substituting the /alue of t in e8. (1 we get

s G (1

2) (>i >f( >fW >iaG

(1

2) (>f >i( >fW >ia

2as G (>f >i ( >f7 >i

(>f >i( >f7 >i G 2as Xusing the identity a2

7 b2

G (a b (a 7 bY=- >i .@@@@@@@@@@@ T,' E?:' M'

A//*


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Ideal Science Academy0alileo was the =rst scientist to obser/e that neglecting the eect of a

resistance all bodies in free7fall close to the 'arthNs surface accelerat

/ertically downwards with the same acceleration4 namely ,.+ m;s2

':ampleIf a ball is thrown /ertically upward it rises to a particular height and then fal

bac5 to the ground. "owe/er this is due to the attraction of the earth whic

pulls the obect towards the groundH

C,/*'.'/ O "** "f is e8ual to Dero

(a G 7,.+m;s2 >fG i is e8ual to Dero (a G ,.+m;s2 >i G


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G 3:1


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Ideal Science Academy(time tG

1

2 minutesG 3fG Q SGQ

y using 1ste8uation of motion4>fG >iat>fG (1 ;2

2aSG > f 2

7> ;2

2(elocity >iG 3


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Ideal Science AcademyP @6) A ' .. 5 ,* *. ', //*elocity >iG


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Ideal Science AcademyI''< *


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Ideal Science Academy1


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Ideal Science AcademyAs we 5now that4

aG (vfvi

t )

aG


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where4

p is the momentum

m is the mass

/ the /elocity

LA2 O" MOTIONS

*ewton formulated three laws of motion in his boo5.

NE2TON "IRST LA2 O" MOTIONS

*ewtonNs =rst law of motion is also 5nown as the %aw of Inertia.

STATEMENT

'/ery body continues its state of rest or uniform motion in a straight line unti

it is acted upon by an e:ternal or unbalance force to change its state of rest or

uniform motionH.


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Ideal Science AcademyEPLANATION

This law consists of a two parts

(a -hen body is at rest

(b -hen body is mo/ing with uniform /elocity(a)@ 2,* '. *.

*ewtonNs %aw states that when a body is at rest it continues its rest unless we

apply a force on it. -hen we apply a force it changes its state of rest and

starts mo/ing along a straight line.

(b 2,* '. 5='> ', :'5 =*


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Ideal Science AcademyEPLANATION

-hen we push a body with greater force then its /elocity increases and chang

of /elocity ta5es place in the direction of the force. If we apply a certain force

on a mass m then it mo/es with certain /elocity in the direction of the force. Ithe force becomes twice then its /elocity will also increase two times. In this

way if we go on increasing the fore there will be increase in /elocity which wil

increase the acceleration.

DERIATION

According to the *ewton\s Second law of motion when a force acts on an

obect it produces an acceleration which is directly proportion to the amount othe force.

a ] F

and in/ersely proportional to the product of mass

a ]1

m

Bombining both.

a ]F

m

A G constant F;m

a G 5F

m

If the >alue of constant 9 is 1


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so

a GF

m

or

F G ma

THIRD LA2 O" MOTION

Statement4

To e/ery action there is always an e8ual and opposite reaction H

EPLANATION

According to *ewtonNs %aw of !otion we ha/e4

F(action G 6 F(reaction

The negati/e (7 sign indicates that the two forces are parallel but in the

opposite direction. If we consider one of the interacting obects as A and the

other as then according to the third law of motion4

F(A G 6 F(AF(A represents the force e:erted on A and F(A is the force e:erted on

.

E5;


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Ideal Science Academy"RICTION

?e=nition

The force which resists the motion of one surface o

another surface is 5nown as

friction.

':planation

Suppose a wooden bloc5 is placed on a table and a spring balance is attache

on it. If we apply a /ery small force of magnitude F by pulling the sprin

gradually and increase it we obser/e that the bloc5 does not mo/e until th

applied force has reached a critical /alue. If F is less then critical /alue th

bloc5 does not mo/e. According to *ewtonNs Third %aw of motion an opposit

force balance the force. This opposing force is 5nown as the force of friction o

friction.

C:.*."'/'

If we see the surface of material bodies through microscope we obser/e tha

they are not smooth. '/en the most polished surfaces are une/en. -hen on

surface is placed o/er another the ele/ations of one get interloc5ed with th

depression of the other. Thus they oppose relati/e motion. The opposition

5nown as friction.

"/. ,'/, "'/' D*;*.

The force of friction depends upon the following factors4

1. *ormal Leaction (L

Force of friction is directly proportional to normal reaction (L which act upon


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Ideal Science Academythe body in upward direction against the weight of the body sliding on the

surface.

2. *ature of Surfaces

Force of friction also depends upon the nature of the two surfaces. It is denoteas u and has constant /alues for e/ery surface. It is dierent for the two

surfaces in contact.

Boe^cient Kf Friction

The coe^cient of friction is a number which represents the friction between

two surfaces. etween two e8ual surfaces the coe^cient of friction will be the

same. The symbol usually used for the coe^cient of friction is 0ree5 letterJ where < _ J _ 1 .

The ma:imum frictional force (when a body is sliding is e8ual to the coe^cien

of friction ` the normal reaction force.

F G J L

-here J is the coe^cient of friction and L is the normal reaction force.

This frictional force F will act parallel to the surfaces in contact and in a

direction to oppose the motion that is ta5ing; trying to ta5e place.

A=>*. "'/'

1. -e could not wal5 without the friction between our shoes and the ground. A

we try to step forward we push our foot bac5ward. Friction holds our shoe to

the ground allowing you to wal5.

2. -riting with a pencil re8uires friction. -e could not hold a pencil in our hand

without friction.

3. A nail stays in wood due to friction

$. *ut and bold hold due to friction


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Ideal Science AcademyDISADANTAES O" "RICTION

1. In any type of /ehicle6such as a car boat or airplane6e:cess friction means

that e:tra fuel must be used to power the /ehicle. In other words fuel or

energy is wasted because of the friction.2. The %aw of Bonser/ation of 'nergy states that the amount of energy remain

constant. Thus the energy that is lostH to friction in trying to mo/e an obect

is really turned to heat energy. The friction of parts rubbing together creates

heat.

3. ?ue to the friction a machine has less e^ciency less than 1


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Ideal Science Academy-hen a body rolls o/er a surface the force of friction is called rolling friction.

Lolling friction is much less than the sliding friction. This is because the

surfaces in contact are /ery much less.

LON QUESTIONSuestion4 ':plain the %aw of Bonser/ation of !omentumQThis law states that

B-hen two or more bodies collide with one another the total momentum of th

system remains the same pro/ided no e:ternal force acts upon them.

E; L /.*=' 55*:5

Total !omentum before collision G Total !omentum after collision

m1u1 m2u2 G m1/1 m2/2

Loc5ets and et engines also wor5 on the same principle. In these machinesot gases produced by burning of fuel rush out with large momentum. Theachines gain an e8ual and opposite momentum. This enables them too/e with /ery high /elocities.

Q:*.' D*+* '/' *./'* ,* ;*. '/'


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Ideal Science Academyuestion4 -hat is force of frictionQ "ow friction can be reducedQ"'/' -The force which resists the motion of one surface on another surface is 5now

as

friction.

M*,. *:/* '/' -i Sliding parts should be highly polished to reduce friction.

ii Friction of li8uids is less than solids. Therefore oil or grease is applie

between the parts of machinery.

iii Lolling friction is less then sliding friction. Therefore sliding friction shoul

be con/erted to rolling friction by using ball bearings.i/ Front side of /ehicles aeroplanes and ships are shaped wedge li5e an

pointed so that minimum friction is oered by air.

C*';*< "/*?e=nitionThe force that causes an obect to mo/e along a cur/e (or a cur/ed path iscalled centripetal force.H!athematical ':pression

-e 5now that the magnitude of centripetal acceleration of a body in a uniform

circular motions is directly proportional to the s8uare of /elocity and in/ersely

proportional to the radius of the path Therefore

a(c ]/2

a(c ] 1;r

Bombining both the e8uations4

a(c ] /2;rFrom *ewtonNs Second %aw of !otion4

F G ma

G F(c G m/2;r


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Page$elocity of obect r G Ladius of the cur/ed path

an5ing of the roadsFactors on which Fc ?epends4

Fc depends upon the following factors4

Increase in the mass will increases Fc.

It increases with the s8uare of /elocity.

It decreases with the increase in radius of the cur/ed path.

-hen a car ta5es':amples

The centripetal force re8uired by natural planets to mo/e constantly round a

circle is pro/ided by the gra/itational force of the sun.

If a stone tied to a string is whirled in a circle the re8uired centripetal force is

supplied to it by our hand. As a reaction the stone e:erts an e8ual force which

is felt by our hand.

The pilot while turning his aero plane tilts one wing in the upward direction so

that the air pressure may pro/ide the re8uired suitable Fc.

C*':>< "/*?e=nition

A force supposed to act outward on a body mo/ing in a cur/e is 5nown a

centrifugal force.H':planation

Bentrifugal force is actually a reaction to the centripetal force. It is a well7

5nown fact that Fc is directed towards the centre of the circle so the

centrifugal force which is a force of reaction is directed away from the centre


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Ideal Science Academyof the circle or the cur/ed path.

A//'> N*. ,' < /* *. / ,*

5='> : /'/


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Ideal Science Academy*et force acting on body AGm1g7T

According to the *ewtonNs law of motion4

m1g7T G m1a ..... ...... 1

As body mo/es upwards hence its weight m2g is less than the tension T ithe string.

*et force acting on body G T 6 m2g

According to *ewton law

T7 m2g G m2a ...... ..... 2

Adding '8.1and '8 2 we get acceleration a.

aG ( m1

m2

m1+m 2 g

?i/ide '8. 2 by '8.1 to =nd tension T in the string.

T G (2m1m2

m1+m2) g ..... ..... 3

The abo/e arrangement is also 5nown as Atwood machine. It can be used t

=nd the acceleration g due to gra/ity using g G (m1

+m2

m1m2

a

KL


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M' '*. /,* ,* *. .'> , ;..*. =*

'/'


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Ideal Science Academytherefore body also mo/es o/er the horiDontal surface with the sam

acceleration a. As the pulley is frictionless hence tension T will be the sam

throughout the string.

Since body A mo/es downwards therefore its weight m1g is greater than thtension in T in the string.

*et force acting on the body A G m1g 6 T

According to the *ewtonNs second law of motion4

m1g 6 T G m1a ... ... ... (1

The forces acting on the body are4

I. -eight m2g of the body acting downwards.II. Leaction L of the horiDontal surface acting on the body in the upwar

direction.III. Tension in the string pulling the body horiDontally on the smoot

surface.

As body has no /ertical motion hence resultant of /ertical forces (m2g and L

must be Dero.

Thus the net force acting on the body is T.According to the *ewtonNs second law of motion4

T G m2a ... ... ... (2

Adding e8s. 1 and 2 we get acceleration aas4

m 1g 6T T Gm1a m2a

m1g G a(m1m2

a Gm1

m1+m2 g ... (3

Putting the /alue of ain e8uations 2 to get tension T as4

T Gm 1m2

m1+m2 g ... ... ... ($


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"ORCE AND THE MOMENTUM

Bonsider a body of mass m mo/ing with initial /elocity >i. %et a force Facts onthe body which produces an acceleration ain it. This changes the /elocity ofthe body. %et its =nal /elocity after time tbecomes >f. if Piand Pfbe the initialmomentum and the =nal momentum related to the body related to the initialand the =nal /elocity respecti/ely then4

Pi G m/i and Pf G m/fBhanges in momentum G Final momentum 6 initial momentumKr Pf 6 Pi G m/f 7 m/i

Thus the rate of change in momentum gi/en by4ppt G

mvmvt

G mvfvi

t

Sincevfvi

t is the rate of change of /elocity e8ual to the acceleration a

produced by the force F.pfpi

t G m a

According to *ewtonNs second law of motion4F G ma

Krpfpi

t G F

'8uation also de=nes the force and states *ewtonNs second aw of motion as4B2,* /* /. % ' ;:/*. //*


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Ideal Science Academy3@G@2, '. ' >*:. ,* :. =*< Ans 4 The friction or drag force due to air acting on the upper part of the bodyof a person standing on the roof of running bus tries to turn o/er which isdangerous while the lower part of body remains at rest w.r.t roof of the bus

3@6@ 2, *. ;..*>* 5=* : ,* :. *. :A. -hen does bus ta5e a turn the passenger sitting inside e:periencedcentrifugal force and mo/es out wards

3@7@H / : *


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Ideal Science AcademyAccording to %aw of conser/ation ofmomentum

Total !omentum before collision G Total !omentum after collision

m1u1 m2u2 G m1/1 m2/2

3@1@2, '. ,* : '. +*% ' */'


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Ideal Science AcademyA.the interloc5ing between ups and down of two surface need not beruptured in case of rolling while in case of sliding these are to be ruptured andresult to increase in friction .3@18@-hat do you 5now about the followingQ

(i T*.' ' .'>A. Tension in string is to neutraliDe applied force on the string this pre/entsit from mo/ing.

(''') L'5''> /* '/'A.The force of friction on the body at rest lying in a rough surface is calledforce of static friction its /alue increases with the increase of applied force .Thema:imum possible /alue of static friction if applied force made grater then itbody starts mo/ing is called limiting force of static friction

('=) $'> /*A.the brac5ing force is the force between bra5e pushing and wheel of

/ehicle. It is help to stop the wheels.(=) S''> =*,'/ .A.the outer edge of road is made higher to pro/ide reactional force on tyre

which pre/ents it from slopping. It is called ban5ing of road.(=''') C*5 .*;Ans4 in a cream separator mil5 is rotated and lighter particles of cream come athe a:is of rotation and are separated from mil5 and collected through thepipe.3@19@2, : 5/,'* '. 5* .;' ,'>,.;**Ans4 at /ery high spinning speed the water and dirt particles are separate fromcloths to clean them inside washing machine.

C,;* N 3 D5'/.


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Ideal Science AcademyP 3@1) A /* 0 N 5=*. ', //* 5


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Page& * /,* ,* * ,* .'>

, ;..*. =* '/'


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Ideal Science Academya G (

m1m2m1+m2 g

a G (&27$+ (1


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Ideal Science Academy(Initial momentum PiG 22*s

PfG

157315472 complete notes on 9th physics by asif rasheed

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