Exam 2 Probtrem 1. Froblem 2. Problem 3. Problem 4. Problem 5

Exam 2

Probtrem 1.

Froblem 2.

Problem 3.

Problem 4.

Problem 5.

February 24, 2&A6

FIRST LETTER OFYOURLA,ST NAME

P$ysics 2760i',t:

{, \.

Show all your work on the problems (notations, diagrams, equafions,

calculations, substitutions, final answer encircled in a box). Give shortexplanation of what you are doing. Academic honesty is presunred.

18 points

18 points

18 points

18 points

18 points

l)

'fu,=t0>

TOTAL: 90 points

Problem 1. A copper penny has a mass of 3 g. What is the total charge of all the electrousin the penny? Hinh the atomic Drrmber of copper is 29, and its atomic weight * Ur,t^3$ *

A<-_- dov A-1 ,b7. L^-Lr h._1._ _64

5J/.^"1 _ ,u _ \.1

^4r21'i' by 5J1"^"1 '" q.f. O7V1 t te /' ' 1/-'o'

,,

, | - ' 09"4 U"r'oti& , 3, ol u[;'l^ta'-'ld^o-.o- "l e t-l , u€"'11 ' Y<

\- J ^/\ r t /.'t , , 13 . - \

a't " W}"?Ji :4" = ],\it v /o, ?Lt^,

LL*,n JQ,' tl, ru ryt,n &uo,) :/:l * r,i*c,

r4frffipon&

/s)K

Problem 2, Charge gl = * 25 nC is at the origirb charge gz= - 15 nC is on the r axis atx = 2nr,andctrarge(tro=* 20nCisatthepointx =2trrt y=Zm.FindtheresultantforceXFonqo

1_, "- 25e -7

C

1r= -lS e-t;

7,,= Ao L'?C

5Y ry ].r^

rMx+W.V.lsi.''1

Y= )gn'>''-

l''Y*:u )xc,.t 'r*

-r\ (J y;' '- / o'

(,'

Tt.*f,(t5{,r} _, .

, )'A'"---J:--' -' -g''l4A

r11 t"so! P''_,^\_-,*-__.-

-

11k, *l:t^ \5" ) t\, b1 %

.os'ls"2 eJL

L,=

d\,}',<.'t,er= 1t

2a"t\' tT1

>t ': ?$,a"t ^2r-v l-=-

6t,l* *'

1,1lL-.:--r?JO

Problem 3. Find the electric fietd on the y axis 8t y = 3 m for the charges shower fu this

figure.

\ a"=+lr2nC\

E-- \JL.9t

?€^ 6 f xe''t\-*(\s-Q, 1 b-51't -;7c''1

ffze",G)ff ::, 53^ \/

r l.d.ir€<'l 1 o u1

' y J.:ut-.-frtur

rLt

L,:

Qilt l-\olc-

7t:€{teE-,Ad

^) \-)) lrl ?){u/,

- lr )?. / L- ".-"._: . -.'

"t4 ttil}\-7 r\J L/ L,fi\,\){,'- r^)

q\Lt ,

t5

Uo\'aL l

t +)fLyy s

&

to u(/^

Problem 4. An inf-ttryt.i;xir"J::'ffi ffi il-rly*;"t;iff l,:;:ff :a;;ffi ,T:;

/

r,Q.j; "){o l, *

fttu fai^{ ,*, .rf

S *.-, f'pc

Ke)Y

',r("rn"IL-t'.P cz t

U'Fo\,r"*ro7,t,^ 1o-5*^

y rto 5a

,Q/u7,^,

Erc/

bi^ 7r" \,

("',4 t'oh', T

tJ

9l.-)zl-4|,."<7-

L\J€J

1e^#(v.c)

-(s.^)F'r /B,Do

E ",fcr + 13

I4/LEr'-

\c

Problem 5. An infinite plane of surface charge density 6-L * 4.5 nCk*lies in the;z plane,

and a second infinite phne of surface charge deruity d-: - 45 nC7m2 lies in in a ptaneparallel to theye plane atx = 2 m" Find the electric field at (a)r = 1.8 m and (b)r = 5 m.

5{,u'1, --

r "[LLs*For- -- ,--

L"

\,X

,/\_/

o.T\ i*{i " tl f /- *- nl . l-*,

3e€ = L' fr,.o,J or'.-J." f,,,

)(. Pceu--<* J

I.: r fb -/Y)(s.g>Enn ff*a\

25'7 +-)51 &