INDICE INTRODUCCION.................................................................3 IMPACTO DE CUERPOS RIGIDOS.........................................4 DIFERENCIA ENTRE EL IMPACTO IMPACTO DE UN CUERPO RÍGIDO Y DE UNA PARTÍCULA... ARTÍCULA.......... ........................... ............................................................ ...................................................... ..............4 4 NOMENCLATURA BÁSICA Y SUPOSICIONES...................................6 CLASIFICACIÓN DE IMPACTOS.......................................................7 IMPACTO CENTRAL.............................................................................8 IMPACTO EXCÉNTRICO.............. ..................... ......................................... ..................................................12 ................12 FASES DEL IMPACTO EXCENTRICO:...........................................13
IMPACTO EXCENTRICO RESTRINGIDO.........................................18
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
IMPACTO ENTRE CUERPOS RIGIDOS U' ),("* :"#$%& &'*3& ! "%&3!< &! %' !%"&! $%& !%&/& *&'&3 /%9(3 &' %' )'*&30(/ & *)&, ,%- "3*. S%&/& )3 (",(( & 5%&3(! & 3&("")+' &'*3& /! "%&3! 3&/(*)0(,&'*& )'*&'!(! / $%& ( /%9(3 ( 5%&3*& "(,)! & 0&/")( & %' (,! "%&3!. L(! )'*&'!(! 5%&3(! & 3&("")+' *(,)=' 3)9)'(' %'( &53,(")+' "'!)&3(/& & /! "%&3! &' "/)!)+' - &' "'!&"%&'")( /( "'0&3!)+' & &'&39( ,&">')"( &' !') - "(/3. "(/3.
DIFERENCIA ENTRE EL IMPACTO DE UN CUERPO RÍGIDO Y DE UNA PARTÍCULA S& (!%,& •
•
•
•
•
•
•
•
S& "'"& &/ "&@")&'*& & 3&!*)*%")+' L(! ,(!(! & /! "%&3! A-B L( !)")+' & !%! "&'*3! & ,(!(! L(! 0&/")(&! 3&0)(! (/ ),("* S%! ,,&'*! 3)'")(/&! & )'&3")( C, &/ ,0),)&'* &! &' &/ /(' /(! 0&/")(&! &!%=! &/ ),("* & /! "%&3! A - B &! %'( )'53,(")+' ",%&!*( & !&)! (3*&! L! ",'&'*&! & /(! 0&/")(&! & /! "&'*3! & ,(!( & A - B :4 )'"+9')*(!< L(! 0&/")(&! ('9%/(3&! & A - B :2 )'"+9')*(!<
IMPACTO ENTRE CUERPOS RIGIDOS PARTICULA • Como no actúan f!"#a$ !%t!"na$ &m'($&)a$* (a cant&+a+ +! mo)&m&!nto (&n!a( +! to+o !( $&$t!ma , +! ca+a PARTICULA con$&+!"a+o &n+&)&+a(m!nt! $! con$!")a.
CUERPO RIGIDO C, ' ("*(' 5%&3(! &?*&3'(! ),%/!)0(! /( "('*)( & ,0),)&'* /)'&(/ - ('9%/(3 & * &/ !)!*&,( - & "(( CUERPO "'!)&3( )')0)%(/,&'*& !& "'!&30(.
• En !( ca$o +! na 'a"t-c(a* (a con$!")ac&n +! (a cant&+a+ +! mo)&m&!nto (&n!a( no$ '"o)!! +! t"!$ !cac&on!$ , (a !cac&n +!( co!/c&!nt! +! "!$t&tc&n !$ (a ca"ta !cac&n.
C, &' &/ "(! & %'( (3*"%/( /( "'!&30(")+' & /( "('*)( & ,0),)&'* /)'&(/ '! 30&& & *3&! &"%(")'&! - /( &"%(")+' &/ "&@")&'*& & 3&!*)*%")+' &! /( "%(3*( &"%(")+'. L(! ! &"%(")'&! 3&!*('*&! !& *)&'&' & /( "'!&30(")+' & /( "('*)( & ,0),)&'* ('9%/(3 *(,)=' &',)'( ,,&'* ")'=*)" *,( (/3&&3 &/ %'* & ),("* O.
Conc($&n E/ ('>/)!)! &/ ),("* & %' "%&3 39) ((& ! &"%(")'&! & "'!&30(")+' & /( "('*)( & ,0),)&'* ('9%/(3 ( /(! "%(*3 $%& !& %!(' &' !)!*&,( & (3*"%/(!. L( *&3( & ),("* $%& !& %!( &! /( ,)!,(.
NOMENCLATURA 01SICA Y SUPOSICIONES E/ ),("* & %' "%&3 39) &! &35&"*(,&'*& />!*)" :& < !) /! "%&3! $%& "/)!)'(' 53,(' &!%=! &/ ),("* %' !/ "%&3 39). U' ),("* &! &/>!*)" !) H & H 1. E/ "(! )&(/ & 1 &! &/ ),("* &35&"*(,&'*& &/>!*)"
A&,>! &',)'(3&,! ( %' ),("* ", ' 3&!*3)'9) !) !3& /! "%&3! $%& "/)!)'(' ' ("*( ')'9%'( 5%&3( ),%/!)0( &?*&3'( & *3 , !& /& &',)'(3> 3&!*3)'9). E/ ),("* & "%&3! 39)! %&& !&3 (!*('*& ",/& ' /),)*(3&,! &' &!*( &?!)")+' ( /! "(!! &' /! $%& /(! !)9%)&'*&! !%!)")'&! !& "%,/&' E/ ),("* ",3&'& ( !/ ! "%&3! &' ,0),)&'* /(' '& ')'9%'( 5%&3( ),%/!)0( *)&'& %'( ",'&'*& &3&')"%/(3 (/ /(' &/ ,0),)&'*.
E/ "'*("* &'*3& /! "%&3! 39)! *)&'& /%9(3 &' %' !/ %'* - &' &!*& %'* !& %&& &@')3 "/(3(,&'*& /( /'&( & ),("*. E/ "'*("* &'*3& /! "%&3! 39)! *)&'& /%9(3 !)' 53)"")+'.
CLASIFICACI2N DE IMPACTOS
Im'acto c!nt"a( E' %' ),("* "&'*3(/ /! "&'*3! & ,(!(! & /! "%&3! $%& "/)!)'(' &!*>' !3& /( /'&( & ),("* :LDI<. (- ! *)! &
),("*! "&'*3(/&! &/ )3&"* - &/ /"%. I'&&')&'*&,&'*& &/ *) & ),("* ( /(! !%!)")'&! $%& !& #(' #&"# (/ )')") &/ ),("* "&'*3(/ & %' "%&3 39) *)&'& ! "(3("*&3!*)"(! ),3*('*&! 1. L(! 0&/")(&! ('9%/(3&! !& "'!&30(' ( *3(0=! & * &/ ),("*. 2. L( &"%(")+' &/ "&@")&'*& & 3&!*)*%")+' %&& !&3 &!"3)*( )3&"*(,&'*& &' *=3,)'! & /! ",'&'*&! & /( 0&/")( ( / /(39 &/( /'&( & ),("* &/ "&'*3 & ,(!(!.
EEMPLO
D&) (/ ),("* "&'*3(/ /( 5%&3( ),%/!)0( N ' 9&'&3( ,,&'*! (/3&&3 & /! "&'*3! C - D L( "'!&30(")+' &/ ,,&'* ")'=*)" 3%"& /(! &"%(")'&!
S& "'"/%-&
C, ' #(- 5%&3(! ),%/!)0(! &' /( )3&"")+' &3&')"%/(3 ( /( /'&( & ),("* /! ",'&'*&! & /( 0&/")( &' &!*( )3&"")+' ' "(,)(' ( "'!&"%&'")( &/ ),("*
A/)"(,! (#3( /( "'!&30(")+' & /( "('*)( & ,0),)&'* & * &/ !)!*&,( ( / /(39 & /( LDI
L( "'!&30(")+' &/ COR &' E - J
A'>/)!)! ")'&,>*)"
E5&"*%('
C,(3(' ",'&'*&! &' /( )3&"")+' ? :LDI<
L( &"%(")+' &/ COR %&& &!"3))3!& (#3( &' *=3,)'! & /( 0&/")( &/ "&'*3 & ,(!(!
A/)"(' /(! "')")'&! )')")(/&! - "'!)&3(' &/ ),("* &35&"*(,&'*& &/>!*)" :& 1< !& *)&'&
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
Im'acto !%c5nt"&co
E/ ),("* &! &?"='*3)" 3$%& (/ ,&'! %' & /! "&'*3! & ,(!( & /! "%&3! $%& "/)!)'(' ' &!*> !3& /( /'&( & ),("*. U' ),("* &?"='*3)" (5&"*( ' !/ /(! 0&/")(&! & /! "&'*3! & ,(!( !)' *(,)=' /(! 0&/")(&! ('9%/(3&! & /! "%&3!. E!*& *) & ),("* "%33& ( ,&'% "%(' %' (,! "%&3! &!*>' 3&!*3)'9)! ( 9)3(3 "' 3&!&"* ( %' && @
FASES DEL IMPACTO E6CENTRICO •
S& !%'& $%& %!* ('*&! & /( "/)!)+' B &!*> 9)3(' &' !&'*) "'*3(3) (/ & /(! ,('&")//(! &/ 3&/ "' 0&/")( ('9%/(3
:;B<1 - /( 0&/")( &/ %'* & "'*("* C %)"( &' A &! :%A<1.. S) /! "%&3! !' /)!! /(! 5%&3(! ),%/!)0(! $%& &&3"&' &'*3& ! &!*>' )3)9)(! ( / /(39 & /( /'&( & ),("*. P3 "'K !)9%)&'*& /( ",'&'*& & 0&/")( &/ %'* C !3& &/ "%&3 B $%& &!*> )3)9)( ( / /(39 & /( /'&( & ),("* &! :0B< ) :;B< 13. D& /( ,)!,( 53,( !3& &/ "%&3 A /( ",'&'*& & 0&/")( :%A<1 ( / /(39 & /( /'&( & ),("* &! :0A<1. P(3( $%& "%33( %'( "/)!)+' :0A<1 :0B<1.
•
D%3('*& &/ ),("* %'( 5%&3( ),%/!)0( P )9%(/ &3 %&!*( $%& &53,( !%! &3@/&! &' &/ %'* & "'*("* &! &&3") &'*3& /! "%&3!. E/ ),%/! 3&!%/*('*& !& ,%&!*3( !3& /! )(93(,(! & ),%/! (3( (,! "%&3!. A0)&3*( $%& /( 5%&3( ),%/!)0( "3&(( &' &/ %'* C !3& &/ "%&3 &' 3*(")+' 9&'&3( 3&("")'&! ),%/!)0(! !3& &/ (!(3 )'!*(/( &' O. S& !%'& $%& &' &!*! )(93(,(! &/ ),("* "3&( 5%&3(! $%& !' ,%"# ,(-3&! $%& /! &!! ' ),%/!)0! & /! "%&3! /(! "%(/&! ' !& ,%&!*3('. C%(' /( &53,(")+' &' &/ %'* C &! %' ,>?), &' (,! "%&3! C !& ,%&0& "' 0&/")( ",' 0 ( / /(39 & /( /'&( & ),("*. E'*'"&! "%33& %' &3) & 3&!*)*%")+' &' &/ $%& /! "%&3! *)&'&' ( 3&"%&3(3 !%! 53,(! 3)9)'(/&!
•
•
L( 5(!& & 3&!*)*%")+' "3&( %'( 5%&3( ),%/!)0( R )9%(/ &3 %&!*( $%& ("*( &'*3& /! "%&3! ", !& ,%&!*3( &' &/ )(93(,( & ),%/!. D&!%=! & /( 3&!*)*%")+' /! "%&3! !& !&(3(' & ,('&3( $%& &/ %'* C !3& &/ "%&3 B *)&'& 0&/")( :0B<2 - &/ %'* C !3& &/ "%&3 A *)&'& 0&/")( :%A<2 '& :0B<2 :0A<2.
E' 9&'&3(/ %' 3/&,( $%& ),/)"( &/ ),("* & ! "%&3! 3&K $%)&3& /( &*&3,)'(")+' & ! )'"+9')*(! :0A<2 - :0B<2 !%')&' $%& :0A<1 - :0B<1 !' "'")(! : $%& %&&' !&3 &*&3,)'((! %!(' ")'&,>*)"( ,=*! & &'&39( /(! &"%(")'&! & ,0),)&'* &*".<. P(3( 3&!/0&3 &!*& 3/&,( &&' &!"3))3!& ! &"%(")'&!. G&'&3(/,&'*& /( 3),&3( &"%(")+' ),/)"( (/)"(3
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
E' /! DCL !& )')"( "/(3(,&'*& /( /'&( & ),("* - &/ !)!*&,( & "3&'((! &!"9). S& &/)9& &/ 3)9&' O & *(/ 53,( $%& ")'")& "' /! %'*! & "'*("* E - J &'*3& /! "%&3! 39)! &' &/ )'!*('*& &/ ),("* - *&'&3 3&!&'*& $%& O &! %' %'* @. D& &!*( 53,( &/ %'* O !&3> &/ %'* ,>! "'0&')&'*& (3( *,(3/ ", "&'*3 & ,,&'*! "%(' !& (/)"( &/ 3)'")) &/ ),%/! ('9%/(3 - ,,&'* ")'=*)". L( !/%")+' & %' 3/&,( & ),("* &?"='*3)" & "%&3! 39)! ' 3&!*3)'9) &!*> 9&3'(( 3 !&)! &"%(")'&! &!"(/(3&!.
L( 3),&3( & &!*(! &"%(")'&! !& &3)0( & /( (/)"(")+' & /( "'!&30(")+' &/( "('*)( & ,0),)&'* (3( * &/ !)!*&,( ( / /(39 & /( /'&( & ),("*
L( !&9%'( - *&3"&3( & &!*(! &"%(")'&! !& &3)0(' *(,)=' & /( (/)"(")+' & /( "'!&30(")+' & "('*)( & ,0),)&'* &' /( )3&"")+' &3&')"%/(3 ( /( /'&( & ),("* "'!&"%&'")( & /( !%!)")+' $%& &/ "'*("* *)&'& /%9(3 !)' 53)"")+'
L( "%(3*( &"%(")+' &! /( &"%(")+' &/ "&@")&'*& & 3&!*)*%")+' /( "%(/ /( &!"3)),! 3),&3 &' *=3,)'! & /! ",'&'*&! & /(! 0&/")(&! &/! %'*! & "'*("* ( / /(39 & /( /'&( & ),("*
E!*( &"%(")+' /( &,! /%&9 3&&!"3))3 &' *=3,)'! & /! ",'&'*&! & /( 0&/")( &/ "&'*3 & ,(!( (!&9%3(' $%& !& !(*)!5(9( /( ")'&,>*)"( &/ !+/) 39) / "%(/ 3&$%)&3& $%&
C, E J - O ")'")&' &' &/ )'!*('*& &/ ),("*
E5&"*%(' /! 3%"*! 0&"*3)(/&! - !%!*)*%-&' !& *)&'&
F)'(/,&'*& &,! 3&&!"3))3 /( &"%(")+' &/ "&@")&'*& & 3&!*)*%")+'
C, /( /'&( & ("")+' & /(! 5%&3(! & "'*("* &'*3& A - B (!( 3 &/ %'* O /(! ! &"%(")'&! 3&!*('*&! 30)&'&' & /( "'!&30(")+' &/ ,,&'* ")'=*)" &/! "%&3! A - B 3&/(*)0! ( O
D+'&
IMPACTO E6CENTRICO RESTRINGIDO E' %' ),("* 3&!*3)'9) %' (,! "%&3! &!*>' !%&*! ( 5%&3(! &?*&3'(! ),%/!)0(!. M&/(3 &!*& *) & ),("*! %&& !&3 (!*('*& ",/& '! /),)*(3&,! (/ !),/& "(! & "%&3! $%& "/)!)'(' 3&!*3)'9)! ( ,0&3!& (/3&&3 & %' && @ & 3*(")+'. E' (!& ( %' &&,/ &?/)"(3&,! &/ 3"&),)&'* ( !&9%)3.
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
D'& &/ 3-&"*)/ !& ,&/( ", (3*"%/( - &/ ='%/ !/ 9)3( (/3&&3 & O.
EERCICIO S
APLICATI7 OS
EERCICIO DE APLICACI2N 8 U'( (33( &!&/*( %')53,& : l=525 mm,W =50 N < &!"('!( !3& %'( !%&3@")& #3)'*(/ &?&'*( & 3(,)&'* - 3&")& &/ ),("* & %' &$%& )!" :
W d =10 N
< !&9' !& )')"( &'
b =75 mm,e= 0.6
/( @9%3( P2 . S) )!" &!
v 0 =4.5 m / s
- /( 0&/")( )')")(/ &/
!&9' %' >'9%/
θ= 60 °
. D&*&3,)'(3
a. L( 0&/")( &/ )!" &!%=! &/ "#$%&. 9. L( 0&/")( &/ "&'*3 & ,(!( & /( (33( &!%=! &/ "#$%&. c. L( 0&/")( ('9%/(3 & /( (33( &!%=! &/ "#$%&. +. L( !)*%(")+' &/ "&'*3 )'!*('*>'& & 3*(")+' & /( (33( %3('*& &/ "#$%&.
SOLUCIÓN: Datos: l =0.525 m
W = 50 N → m =5.097 kg
e =0.6
v 0 =4.5 m / s
W d =10 N → md =1.019 kg
G
G F
F
I G =
1 12
2
.m.r =
1 12
2
2
( 5.097 ) . (0.525 ) =0.117 kg.m
EJE « Y » : TEOREMA CANTIDAD DE MOVIMIENTO
0ARRA
L y : mv Gy + Ft = m vGy
+ =5.097 v Gy
0 0
DISCO
L y : mv dy + Ft = m v dy
∗4.5 sin 60+ 0= 1.019 v dy
1.019
EJE « X » : PARA EL SISTEMA
T!o. Cant. Mo).
∗4.5∗cos 60+ 0 =1.019 v dx + 5.097 v Gx
1.019
T!o. Mom. C&n.
∗1.019∗4.5∗cos 60+ 0= 0.1875∗1.019 v dx + 0.117 ω
0.1875
0.1911 v dx
+ 0.117 ω= 0.43 … … (b )
POR CONDICION :
e=
−( v Gx + 0.1875 ω )− v dx = 0.6 0− 4.5∗cos 60
( vGx + 0.1875 ω − v dx=1.35 … … (c ) DE LAS ECUACIONES a, b y c:
v dx =−0.1344
m m = 0.1344 ← s s
v Gx =0.4780
m s
ω =3.902 rad / s
a V!"oc#$a$ $!" $#sco $!s%&'s $!" c(o)&!. v d =√ 0.1344
2
2
+ 3.897 =3.900 m / s
b V!"oc#$a$ $!" c!*t+o $! asa $! "a ba++a $!s%&'s $!" c(o)&! v Gx =0.4780 m / s
c V!"oc#$a$ a*-&"a+ $! "a ba++a $!s%&'s $!" c(o)&! ω =3.902 rad / s
$ La s#t&ac#.* $!" c!*t+o #*sta*t/*!o $! +otac#.* $! "a ba++a $&+a*t! !" c(o)&! v Gx =ω∗ d
0.4780
=3.902∗d
d =122.5 mm
EERCICIO DE APLICACI2N : L( &!5&3( A & 2 9 !& ,%&0& #(")( /( &3&"#( ( 1 ,! "%(' 9/&( &/ &?*3&, & /( (33( &/9(( B & 4 9 "%- ,0),)&'* ' &!*> 3&!*3)'9). E/ "&@")&'*& & 3&!*)*%")+' &/ ),("* &! & .6. QC%>/&! !' /! 0(/3&! & /( 0&/")( & /( &!5&3( - & /( 0&/")( ('9%/(3 & /( (33( &!%=! &/ ),("*
DESARROLLO E/ ,,&'* ('9%/(3 (3( &/ !)!*&,( !& "'!&30( (/3&&3 &/ "&'*3 & ,(!( & /( (33(.
E/ "&@")&'*& & 3&!*)*%")+' !& %*)/)( (3( 3&/(")'(3 /(! 0&/")(&! 3&/(*)0(! ('*&! - &!%=! &/ ),("*.
E/ ,,&'* /)'&(/ !& "'!&30( (3( &/ !)!*&,(.
L( !/%")+' &'"'*3(,! 3&&,/((' /(! &"%(")'&! &' *3(!. E"%(")+' 1
•
E"%(")+' 2
•
E"%(")+'
•
R&&,/((,! /( &"%(")+' 1 &' /( &"%(")+' 2
R&&,/((,! &!*& 3&!%/*( &' /( &"%(")+'
O*&') &/ 0(/3 & /( 0&/")( ('9%/(3 & /( (33( &!%=! &/ ),("* "(/"%/(3&,! /( 0&/")( & /( &!5&3( /%&9 &/ ),("*.
EERCICIO DE APLICACI2N 3 E/ 0)&'* "(!)'( $%& &/ (3" & 6*'&/((! )/%!*3( !& ,%&0( /&'*(,&'*& ( 1 )& s - 9/&& &/ ,%&//& @ &' P. E/ ,,&'* & )'&3")( & /( ,(!( &/ (3" 3&!&"* ( !% "&'*3 & ,(!( &! & 3 x 10 slug − pe - &/ "&@")&'*& & 3&!*)*%")+' &/ ),("* &! e =0.2 QC%>/ &! /( 0&/")( ('9%/(3 &/ (3" &!%=! &/ ),("* 2
8
2
EJERCICIO DE APLICACIÓN 4 La barra esbelta de 10lb mostrada cae del reposo en la posición vertical y golpea el tope liso en B. El coeficiente de restitución del impacto es e = 0.6, la duración del impacto es 0.1 s y b = 1 pie. Determine la fuerza media eercida sobre la barra en B debido al impacto .
DESARROLLO
Elegimos un sistema con el origen de coordenadas en ! y el ee de las "#$ paralelo a la superficie plana y el ee "y$ %acia arriba. La estrategia consiste en&
(< U!(,! &/ 3)'")) &/ *3(( - /( &'&39( (3 "(/"%/(3 /( 0&/")( ('*&! &/ ),("*
Donde el signo negativo en la ra'z cuadrada es elegido para ser compatibles con la elección de las coordenadas.
< C' &/ "&@")&'*& & 3&!*)*%")+' "(/"%/(,! /( 0&/")( &!%=! &/ ),("*.
D'& v ! - v " ! !' /(! 0&/")(&! & /( (33( ( %'( )!*('")( & %' ),("* ('*&! - &!%=!. D( $%& /(
3-&"")+' & B &! )',+0)/ ('*&! - &!%=! &/ ),("* v #= v " #= 0 . E'*'"&!
"< E/ 3)'")) & ),%/! &/ ,,&'* ('9%/(3 '! (-%(3> ( &*&3,)'(3 /( 5%&3( ,&)( & ),("*.
Donde
F #
es la fuerza eercida sobre la barra en (, de tal )ue&
EERCICIO DE APLICACI2N ; E/ 0)&'* "(!)'( $%& &/ (3" & 6 *' )/%!*3( !& ,%&0( /(*&3(/,&'*& ( 1 )&! - 9/&& &/ ,%&//& @ &' P. E/ ,,&'* & )'&3")( & ,(!( &/ (3" 3&!&"* ( !% "&'*3 & ,(!( &! & ? 18 !/%9K)&2 - &/ "&@")&'*& & 3&!*)*%")+' &/ ),("* &! & .2. QC%>/ &! /( 0&/")( ('9%/(3 &/ (3" &!%=! &/ ),("*
DESARROLLO
E/ ,,&'* ('9%/(3 !& "'!&30( (/3&&3 & P
C'0)3*)&' 6 *'122 774.6 / 417.6 !/%9
E/ "&@")&'*& & 53)"")+' &!
D'& v $ p &! /( ",'&'*& 0&3*)"(/ & /( 0&/")( & P &!%=! & $%& &/ ),("*. L(! 0&/")(&! 0 - 0 &!*>' 3&/(")'(! 3
EERCICIO DE APLICACI2N < U'( &!5&3( & 2 9 $%& !& ,%&0& #3)'*(/,&'*& #(")( /( &3&"#( "' %'( 0&/")( )')")(/ & ,! 9/&( &/ &?*3&, )'5&3)3 & %'( (33( 39)( AB & 8 9. L( (33( !& !%!&'&
& %'( (3*)"%/(")+' &' A - &!*> )')")(/,&'*& &' 3&!. S) &/ "&@")&'*& & 3&!*)*%")+' &'*3& /( (33( - /( &!5&3( &! & .8 &*&3,)'& /( 0&/")( ('9%/(3 & /( (33( - /( 0&/")( & /( &!5&3( )',&)(*(,&'*& &!%=! &/ ),("*.
SOLUCIÓN P3)'")) &/ ),%/! - /( "('*)( & ,0),)&'*.KL( (33( /( &!5&3( !& "'!)&3(' ", %' !/ !)!*&,( - !& &?3&!( $%& /( "('*)( & ,0),)&'* )')")(/ & /( (33( - /( &!5&3( /! ),%/!! & /(! 5%&3(! &?*&3'(! !' &' "'%'* &$%)/&'*&! ( /( "('*)( & ,0),)&'* @'(/ &/ !)!*&,(. S& (0)&3*& $%& /( ')"( 5%&3( ),%/!)0( &?*&3'( (/ !)!*&,( &! /( 3&("")+' ),%/!)0( &' A.
∑ m%me&t%s alreded%r de ! : m s v ' ( 1.2 m )=ms v " s ( 1.2 m) + m ( ´v " ( ( 0.6 m ) + I´ ) "
:1<
P%&!* $%& /( (33( 9)3( (/3&&3 & A !& *)&'& $%& v´ " (=´r ) " =( 0.6 m ) ) "
A&,>! ´= I
1 12
mL
2
=
1 12
2
( 8 kg ) ( 1.2 m ) =0.96 kg.m
2
A/ !%!*)*%)3 &!*! 0(/3&! - /! (*! 33")'(! &' /( &"%(")+' :1< !& *)&'&
( )
( 2 kg ) 5 m ( 1.2 m )=( 2 kg ) v " s ( 1.2 m ) +( 8 kg ) ( 0.6 m ) ) " ( 0.6 m )+ ( 0.96 kg.m ) ) " 2
s
=2.4 v " s + 3.84 ) "
12
:2<
V&/")(&! 3&/(*)0(!. E/)9)&' ", !)*)0 &/ !&'*) #(")( /( &3&"#( !& &!"3)& v " #− v " '= e ( v s− v # )
A/ !%!*)*%)3
v s =5 m / s
v #=0 y e =0.80
v " #− v " s=0.80 ( 5 m/ s )
!& *)&'& :<
A/ '*(3 *3( 0& $%& /( (33( 9)3( (/3&&3 & A !& &!"3)& v " #=( 1.2 m ) ) "
:4<
A/ 3&!/0&3 /(! &"%(")'&! :2< ( :4< & ,('&3( !),%/*>'&( !& *)&'&