2. FORCE
A PUSH OR PULL
ON A BODY I S
CALLED FORCE.
FORCES ARE USED
I N OUR EVERYDAY
ACTI ONS LI KE
PUSHI NG,
PULLI NG,
LI FTI NG,
STRECHI NG,
TWI STI NG AND
PRESSI NG.
3. EFFECTS OF FORCE
• A f or ce cannot be seen. A f or ce can
be j udged onl y by t he ef f ect s whi ch
i t can pr oduce i n var i ous bodi es ( or
obj ect s) ar ound us.
1. A f or ce can move a st at i onar y body.
2. A f or ce can st op a movi ng body.
3. A f or ce can change t he speed of a
movi ng body.
4. A f or ce can change t he di r ect i on of a
movi ng body.
5. A f or ce can change t he shape and si ze
of a body.
4. Types Of For ces
THERE ARE TWO KI NDS OF
FORCES:
1. BALANCED FORCE.
2. UNBALANCED FORCE.
5. BALANCED FORCES
1. I f t he r esul t ant of al l t he
f or ces act i ng on a body i s
zer o, t he f or ces ar e cal l ed
bal anced f or ces.
2. I f a number of bal anced
f or ces act on a st at i onar y
body, t he body cont i nuous t o
r emai n i n i t s st at i onar y
posi t i on.
3. I f a number of bal anced
f or ces act on a body i n
uni f or m mot i on, t he body
cont i nuous t o be i n i t s st at e
of uni f or m mot i on.
4. Though bal anced f or ces cannot
pr oduce mot i on i n a
st at i onar y body but can
change t he shape of t he body.
6. UNBALANCED FORCE
I f t he r esul t ant of al l
t he f or ces act i ng on a
body i s not zer o, t he
f or ces ar e cal l ed
unbal anced f or ces.
When an unbal anced
f or ce act s on a body, i t
pr oduces mot i on i n t he
body. Al so, an
unbal anced can st op a
movi ng body.
I f t her e wer e no
unbal anced f or ce of
f r i ct i on or ai r
r esi st ance, a movi ng
body woul d go on f or
ever .
7. NEWTON’ S LAWS OF MOTI ON
NEWTON HAS GI VEN
THREE LAWS OF TO
DEFI NE THE MOTI ON OF
BODI ES. THESE LAWS
ARE KNOWN AS NEWTON’ S
LAWS OF MOTI ON.
8. NEWTON’ S FIRST LAWOF
MOTION
A body at r est wi l l
r emai n i n r est , and a body
i n mot i on wi l l cont i nue i n
mot i on i n a st r ai ght l i ne
wi t h uni f or m speed, unl ess
i t i s compel l ed by an
ext er nal f or ce t o change
i t s st at e of r est or of
uni f or m mot i on.
I NERTI A: I ner t i a i s t hat
pr oper t y of a body due t o
whi ch i t r esi st s a change
i n i t s st at e of r est or of
uni f or m mot i on.
9. MOMENTUM
The moment um of a body i s def i ned as
t he pr oduct of i t s mass and
vel oci t y.
NOTE: t he f or ce r equi r ed t o st op a
movi ng body i s di r ect l y pr opor t i onal
t o i t s mass and vel oci t y.
Thus, moment um= mass x vel oci t y
or , p= m x v
wher e p= moment um
m= mass of t he
body and,
v = speed of t he
body
SI UNI T= t he SI uni t of moment um i s
ki l ogr am met er s per second ( kg. m/ s)
10. NEWTON’ S SECOND LAWOF
MOTION
The r at e of change of moment um
of a body i s di r ect l y
pr opor t i onal t o appl i ed f or ce,
and t akes pl ace i n t he
di r ect i on i n whi ch f or ce act s.
For ce= change i n moment um/ t i me
t aken
f = mv- mu/ t
f = m( v- u) / t . But we know
t hat v- u/ t =a
f = m x a
f or ce = mass x accel er at i on
SI UNI T: i t s SI uni t i s
‘ f or ce’ .
11. NEWTON’ S THIRD
LAWOF MOTION
Whenever one body exer t s a f or ce on
anot her body, t he second body exer t s
equal and opposi t e f or ce t o t he f i r st
body. OR,
To ever y act i on t her e i s equal and
opposi t e r eact i on.
1. EX: t he r ocket wor ks on t he
pr i nci pal of act i on and r eact i on.
2. When a bul l et i s f i r ed f r om t he
gun, a f or ce sendi ng t he bul l et
f or war d i s equal t o t he f or ce sendi ng
t he gun backwar d. But due t o hi gh
mass of t he gun, i t moves onl y a
l i t t l e di st ance backwar d and gi ves
j er k.
12. CONSERVATION OF
MOMENTUM
When t wo or mor e bodi es
act upon one anot her ,
t hei r t ot al moment um
r emai ns const ant
pr ovi ded no ext er nal
f or ces ar e act i ng.
Moment um i s nei t her
cr eat ed nor dest r oyed.
Tot al moment um bef or e
col l i si on = t ot al
moment um af t er
col l i si on
