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Physics 2220
Spring 2012
Ben Bromley
EXAM 1
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Discussion Instructor:
U __ __ __ __ __ __ __
Chad
Jon Paul
Maria
Peter
Physics 2220
Spring 2012
Ben Bromley
Data: Use these constants (where it states, for example, 1 ft, the 1 is exact for significant figure purposes).
1 ft = 12 in (exact)
1 m = 3.28 ft
1 mile = 5280 ft (exact)

x


x 2  a 2 dx 
1
3

x2  a2

3
1 hour = 3600 sec = 60 min (exact)
1 day = 24 hr (exact)
2
2
gearth = 9.80 m/s = 32.2 ft/s
gmoon = 1.67 m/s2 = 5.48 ft/s2






dx
 x2  a2 
3

x
a2 x2  a2
1 year = 365.25 days
  ax
e
dx


1 kg = 0.0685 slug
1 N = 0.225 pound
1 horsepower = 550 ft‫ڄ‬pounds/s (exact)
24
Mearth = 5.98 × 10 kg
Rearth = 6.38 × 103 km






Msun = 1.99 × 1030 kg





Rsun = 6.96 × 108 m
22
Mmoon = 7.35 × 10 kg
Rmoon = 1.74 × 103 km
G = 6.67 × 10-11 N‫ڄ‬m2/kg2
9
2
2
k = 8.99 × 10 N‫ڄ‬m /C





εo = 8.85 × 10-12 F/m
eelectron charge = -1.60 × 10-19 C
melectron = 9.11 × 10-31 kg





μo = 4π × 10-7 T‫ڄ‬m/A (exact)
N(Avogadro's No.) = 6.02 × 1023 atoms/gm‫ڄ‬mole
26
= 6.02 × 10 atoms/kg‫ڄ‬mole
cos(a ± b) = cos a cos b ‫ ט‬a sin b
xdx
 x2  a 
2 3/2
xdx
a2  x2

1
x2  a2
  a2  x2
dx
 n  x  x 2  a 2 


x2  a2
1  a  x 2  a 2
  n
a 
x
x x2  a2

dx
x a





x
x
 sin 1   , or  cos 1  
a
a
a2  x2
xdx
2
2
 x2  a2
dx
sin(a ± b) = sin a cos b ± sin b
mproton = 1.67 × 10−27 kg
h = 6.64 × 10-34 J
π = 3.14
8
c = 3.00 × 10 m/s









1 Tesla = 10,000 gauss (exact)
ρ(H2O) = 1000 kg/m3
1
  eax
a









dx
1
 n  a  bx 
a  bx b
dx
 a  bx 2

1
b  a  bx 
Physics2220
2220
Physics
Spring 2012
Fall 2009
Name: __________________________________
Unid: ___________________________________
Discussion TA: ___________________________
Exam 1
Show all work!! Report all numbers to three (3) significant figures.
A.
[17 pts.] A car (mass m = 1000 kg and charge q = +7.2 C)
is at rest in a driveway. A uniform electric field (strength
E = 5000 N/C) is turned on to propel the car toward the
street, a distance x = 10 m from the car’s starting point.
Find the car’s speed v when it reaches the street. Assume
that the car acts like a point charge. B. [16 pts.] A simple model of the hydrogen atom consists of an electron in a circular orbit of
radius r = 5.29 × 10
the proton.
-11
m about a stationary proton. Find v, the speed of the electron around
Ben Bromley
1
Physics2220
2220 Fall 2009
Physics
Spring 2012
Name: __________________________________
Unid: ___________________________________
Discussion TA: ___________________________
Exam 1
Show all work!! Report all numbers to three (3) significant figures.
A.
[16 pts.] Find the electric field vector E, evaluated at point P [(x,y) =
(1,1) m], that arises from the point charges shown in the figure. B.
[16 pts.] A straight wire segment of length L, aligned on the y-axis and centered
2
2 3/2
at the origin, has a linear charge density is λ(y) = C [y + a ] , where C is a
constant. Find the strength of the electric field at a point located distance a a
from the wire on the x axis.
Ben Bromley
2
Physics2220
2220
Physics
Spring 2012
Fall 2009
Name: __________________________________
Unid: ___________________________________
Discussion TA: ___________________________
Exam 1
Ben Bromley
3
Show all work!! Report all numbers to three (3) significant figures.
An infinitely long, straight coaxial cable has a thin wire running along its axis surrounded by a
conducting cylindrical pipe of inner radius ri and outer radius ro. The pipe is electrically neutral,
while the wire carries a uniform charge, with linear charge density λ.
(a)
[7 pts.] Write the E field strength just outside the outer surface of the conducting pipe
(r → ro) in terms of the surface charge density η.
(b)
[8 pts.] Find the strength of the electric field E outside of the coaxial cable at a distance r > ro from the cable’s
axis.
(c)
[9 pts.] Find the surface charge density η on the pipe’s outer surface in terms of radius ro and λ.
(d)
[10 pts.] Find the electric field E´ outside the pipe (r > ro) if the wire was removed and the
pipe was filled entirely with a medium of uniform charge density ρ.