understanding gravity - physics form 4

7/24/2019 Understanding Gravity - PHYSICS FORM 4

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-Acceleration Due to

Gravity.-Gravitational Field.

-Gravitational Field

UNDERSTANDING

GRAVIT


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!et"# te#t your $e$ory %

I& you thro' an o()ect* 'hat 'illha++en,

The o()ect 'ill &alling do'nWhat i# Ne'ton"# Second !a',Ne'ton #tated the relation#hi+

(et'een &orce* $a## andacceleration.

F$a


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The a++le #tory


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GRAVITIntroduce# (y Sir I#aac Ne'ton.()ect# &all (ecau#e they are

+ulled to'ard# the Earth (y the

&orce o& gravity.


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keeps things on the

earth.

pull of gravitational forc


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brings things down to earthwhen they are thrown upwards.

e pull of gravitational for


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holds the moon in itsorbit round the Earth.

e pull of gravitational for


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keeps things on the earth.brings things down to earthwhen they are thrown

upwards.holds the moon in its orbitround the Earth.

force, F/


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A00E!ERATIN DUE T GRAVIT

Figure #ho'# a #tro(o#co+ic+hotogra+h o& a (all &allingunder gravity

The di#tance (et'een t'o#ucce##ive i$age#increa#e#* #ho'ing that the

(all are &alling 'ithincreasing velocity , i.e.*&alling 'ith an acceleration


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The acceleration o& o()ect# &alling &reely i# 1no'na# the acceleration due to gravity, g = 10 ms

!2value &ro$ e3+eri$ent4.

There&ore* F $g


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A00E!ERATIN DUE TGRAVIT

n the late 56thcentury* GalileoGalilei dro+# t'o o()ect o&

di7erent $a## &ro$ the !eaningTo'er o& 8i#a and &ound out thatthe o()ect &all 'ith the #a$e

acceleration 2hit the ground atthe #a$e ti$e4 .

Thi# e3+eri$ent to di#+rove

Ari#totle9# theory o& gravity* 'hich
http://en.wikipedia.org/wiki/Aristotlehttp://en.wikipedia.org/wiki/Aristotle


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The !eaning To'er o& 8i#a 2Italy4


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()ect# 'ith di7erent $a##'ould &all 'ith sameacceleration a##u$ing thatthere i# no air re#i#tance

In other 'ord#* gravitationalacceleration i# independentof mass.


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:!E inventedvacuu$ +u$+ tore$ove air.

In vacuu$* (oth

o()ect# reach the(otto$ o& thecylinder at the

#a$e ti$e.In at$o#+here* a

+iece o& ti##ue

+a+er doe# not


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E3+eri$ent in the $oon to te#t Galelio"# #tate$ent

:UT; WE 0ANT D thi# te#t in the earth

(ecau#e there are air re#i#tance 'hicho o#e# the ullin &orce o& ravit .


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A freefalling o()ect i# ano()ect &alling under the &orce o&gravity only.

A &ree-&alling o()ect doe# notencounter other &orce# li1e airresistance or friction that

'ould o++o#e it# $otion

FREE FA!!


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!et"# #ee the e7ect o& air re#i#tance'ith $a1ing our o'n #$all +arachute

"hysics behind the parachute #

Every o()ect 'ill &all do'n 'ith

acceleration o&

.The +arachute e3+erience# the air

re#i#tance and o++o#e# the +ulling &orce o&gravity.

Air re#i#tance e3+erience# (y an o()ectde+end# on it# #ha+e.


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$ravitational %eld is a regionaround the Earth in which an

ob&ect e'periences a force

towards the centre of the earth.

F()*E (F$)+-TF()*E (F

$)+-T

F()*E (F

$)+-T

F()*E (F$)+-T

GRAVITATINA! FIE!D


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The gravitational %eldstrength i# de?ned a# the

force acting on unit mass inthe ?eld.

The gravitational ?eld #trength

at the surfaceo& the Earthi#/. kg1.

g = F2m /

F Gravitational &orce

GRAVITATINA! FIE!DSTRENGT@


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WEIG@T* WThe 'eight o& an o()ect i#de?ned a# the gravitational&orce acting on the o()ect.

F $a

W $g3nit is the same as force, E'ample # ! kg = !0

g is thegravitationalaccelerati

on


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EAB8!E 5A $ar(le i# dro++ed &ro$the to+ o& a (uilding and

ta1e# > # to reach the#ur&ace o& the Earth. Whati# the height o& the(uilding ,

2>C $4


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A roc1 ha# a $a## o&>C.C 1g and 'eight o&


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understanding gravity - physics form 4

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