Physics 9B
Practice Exam
There
are
six
problems.
Work
on
the
test
for
an
hour
and
we
will
go
over
it.
[1]
A
threedimensional
model
of
a
molecule
treats
the
atoms
as
point
particles
located
at
the
corners
of
a
cube
and
connected
by
massless
rigid
rods.
a)
(6
pts)
List
the
degrees
of
freedom
this
molecule
has.
b)
(14
pts)
If
3
moles
of
a
gas
of
these
molecules
undergoes
an
adiabatic
expansion
from
a
pressure
of
5.0
atm
and
a
volume
of
1.0
L
to
a
volume
of
3.0
L,
find
the
final
pressure.
[2]
A
transverse
wave
on
a
string
is
described
by
y
=
3 mm
(
)
cos
π
m
−
1
(
)
x
−
9
π
s
−
1
(
)
t
(
)
.
At
t
=
0,
find
the
position
at
which
the
transverse
velocity
of
the
string
is
a
maximum
and
positive.
[3]
A
spherical
source
of
water
emits
water
at
a
constant
rate
of
5.0
m
3
/s.
Derive
an
expression
for
the
velocity
of
the
water
flow
at
a
distance
r
from
the
center
of
the
source.
Assume
no
mass
loses
and
use
conservation
of
mass.
For
water
®
=
1000.0
kg/m
3
[4]
In
a
double
slit
experiment
the
separation
distance
between
the
centers
of
the
slits
is
five
times
the
width
of
each
slit.
Find
the
ratio
of
the
intensity
of
the
third
interference
maximum
relative
to
intensity
of
the
central
maximum.
You
are
to
assume
the
double
slit
interference
pattern
is
modulated
by
the
single
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 Fall '08
 Cheng
 Physics, Chemistry, Thermodynamics, Electron, Mass, Work, Heat, Wavelength, Doubleslit experiment, Wave mechanics

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