lecture 2 - engineering science

8/16/2019 Lecture 2 - Engineering Science

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2/26

Recap

• Defne scalar

• Defne vector

• Defne Speed and Distance

• Defne Velocity and Displacement

• Explain the dierence !et"een Speed and el$cit%&'antitie(

• State the ad)antage( $* )ect$r $)er (calar


3/26

In thi( lect're+ %$' "ill learn,

• -e"t$n.( La"( $* /$ti$n

• Applicati$n $* -e"t$n.( La"( $* /$ti$n

• Sec$nd La" $* 0$ti$n

• Applicati$n $* Sec$nd La" $* 0$ti$n

• E&'ati$n $* 0$ti$n 1r$$*

• ra)it%


4/26

-e"t$n.( La"( $* 0$ti$n


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The 0ain Rea($n

The e((ence $* the(e la"( i( that in $rder t$ change t/$ti$n $* a !$d% %$' /'(t accelerate it $r decelerate!% appl%ing a *$rce t$ it3 4hen %$' appl% a *$rce t$ a!$d%+ it al($ applie( an e&'al and $pp$(ite *$rce t$ %

•


6/26

The La" $* Inertia

The I-ERTIA $* a !$d% i( the pr$pert% that ena!le( it re(i(t change( in it( /$ti$n3


7/26


8/26

Q'e(ti$n

A r$c8et $* /a(( 2


9/26

THE E;;ECT 5; ;RICTI5-

Friction is an external force that always acts tooppose motion.

4hen a !$d% i( accelerated+ the *$rce ca'(ingaccelerati$n i( the NET FORCE.

Net Force = Applied Force Friction Force


10/26

Calc'late the accelerati$n

The applied *$rce $n a )ehicle i( >


11/26

E&'ati$n( $* /$ti$n *$r 'ni*$r/accelerati$n

E&'ati$n( $* /$ti$n *$r 'ni*$r/ accelerati$n

a)erage )el$cit% 7 )'92accelerati$n a 7 )F'9t

( 7 't G at2

)2 7'22a(

"here ' i( the initial )el$cit%+ ) the fnal )el$cit%+ a thaccelerati$n+ t the ti/e ta8en and ( the di(place/en


12/26

E&'ati$n( $* /$ti$n pr$$*

In (t'd%ing the /$ti$n $* $!ect(+ it i( $*ten help*'l t$an e&'ati$n t$ "$r8 $'t the )el$cit%+ accelerati$n $r di(tance tra)elled3

4e '(e the *$ll$"ing letter( t$ repre(ent certain&'antitie(,


13/26

3 -$n accelerated /$ti$n i3e3 /$ti$n at a c$n()el$cit%

The area 'nder the line $* the )el$cit%Jti/e graph i( the di(tanctra)elled !% the $!ect in the ti/e t3

;$r exa/ple ' 7 2


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23 Accelerated /$ti$n


15/26


16/26

1r$!le/

A h$r(e accelerate( (teadil% *r$/ re(t at K /(F2

*$r =

4hat i( it( fnal )el$cit% and h$" *ar ha( it tra)elled

a Initial )el$cit% ' 7 < ;inal )el$cit% ) 7


17/26

S$l'ti$n

Accelerati$n a 7 K /(F2

Ti/e t 7 = (3

Mn$"n &'antitie( '+a and t3 Un8n$"n )3

C$rrect e&'ati$n i( ) 7 ' at

;inal )el$cit% ) 7 < Kx= 7 2 /(F

! C$rrect e&'ati$n i( ( 7 't G at2

Di(tance ( 7


18/26

1r$!le/

23 A car tra)elling at 2< /(FI

accelerate( (teadil% at ?2 *$r a di(tance $* @< /3 4hat i( the fnal )el$cit% $* tcar


19/26

S$l'ti$n

Mn$"n &'antitie( '+a and (3 Un8n$"n )3

C$rrect e&'ati$n i( )2 7 '2 2a(

;inal )el$cit%2 )2 7 =


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RAITY

All !$die( exert a *$rce $* attracti$n $n each $ther !'thi( *$rce di/ini(he( "ith di(tance3 Unle(( $ne $* the!$die( i( )er% large and9$r )er% cl$(e+ the eect i( )e(/all3 In the ca(e $* the Earth+ it i( large and "e are c($ it exert( a *$rce $* gra)it% $n e)er%thing cl$(e t$ it('ch that an% 'nre(trained !$d% "$'ld accelerated$"n"ard( t$"ard( the centre $* the Earth at N3O /


21/26

RAITY

Thi( i( the gra)itati$nal c$n(tant PgP3allile$ (h$"ed that large and (/all !$die( *all at the(a/e rate "ith hi( *a/$'( experi/ent "hen he dr$ppt"$ cann$n !all( $* dierent (ie( *r$/ the leaning t$$* 1i(a3 The% hit the gr$'nd t$gether3


22/26

Thi( experi/ent "$r8( *$r c$/pact /a((e( !'t i* %$'dr$pped a (panner and a *eather+ the *eather "$'ld ar$'nd $n the air c'rrent(3

Astronauts on the moon showed that in the absenceair,

a spanner and a eather all together.

4atch the ide$


23/26

Since all !$die( are accelerated d$"n"ard( at the (arate then the *$rce acting $n it i( ; 7 0 g3

In $rder t$ (t$p a !$d% *alling+ an e&'al and $pp$(ite*$rce 'p"ard( /'(t !e applied3 Thi( i( '('all% exertethe gr$'nd $n all (tati$nar% !$die( and gi)e( ri(e t$ tidea $* "eight3 The "eight $* a !$d% i( (i/pl% the *$r

gra)it% acting $n it ($

!eight = M g.


24/26

I* a !$d% /$)e( in a )ertical directi$n+ the *$rce re&'/'(t incl'de the *$rce $* gra)it%3

; 7 0a 0g 7 0a g and

accelerati$n a. i( p$(iti)e "hen 'p"ard(3


25/26

;$r a h$)ering aircra*t a 7 < and the 'p"ard( *$rce i(e&'al t$ it( "eight3 A !$d% accelerating 'p"ard( /'(exert a *$rce greater than it( "eight3 A !$d% accelerad$"n"ard( /'(t exert a *$rce le(( than the "eight3


26/26

Q'e(ti$n(

•

Calc'late the *$rce re&'ired *r$/ a r$c8et engine i* /'(t accelerate the r$c8et 'p"ard( at = /9(23 The/a(( i( ?

lecture 2 - engineering science

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