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Unformatted text preview: © Prep101 http://www.prep101.com/freestuff PRACTICE PHYSICS 101 EXAM
Problem 1
I. A student, holding a 500 Hz tuning fork, is walking at 1.50 m/s on a
direct line between two parallel smooth reflecting walls. What
frequency of sound are heard by the student?
II. A column of air in a tube is found to have standing waves at
frequencies of 380, 532 and 684 Hz. There are no standing wave
frequencies between the above frequencies.
a) What is the fundamental frequency of the tube?
b) Is the tube open at both ends or open at one end and closed
at the other end?
c) Draw a displacement curve for the 532Hz standing wave.
d) the air in the tube is now replaced with carbon dioxide which
has a speed of sound of 280m/s. What are the new
frequencies corresponding to the given standing wave
frequencies? Page 1 of 7 © Prep101 http://www.prep101.com/freestuff Problem 2
Two flat glass plates, each of length 6.0cm, are
separated at each end by two support of
thickness t1=0.00125 mm and t2=0.00575 mm,
as shown in the figure. The air between the
glass plates forms a thin film. Green laser light
of wavelength 500 nm is incident from the top.
When viewed from above, an interference
pattern consisting of alternating bright and dark
fringes is observed. t1 t2 6.0 cm a) What is the separation of the two dark fringes? b) What must be the index of refraction of a 150 nm thick
coating (with index of refraction less than 1.5) on a glass
surface (n=1.5) if it is to eliminate reflection of 650 nm light
incident on the coating from air? Page 2 of 7 © Prep101 http://www.prep101.com/freestuff Problem 3
I. A hydrometer consists of a spherical bulb with a cylindrical stem.
The crosssectional area of the stem
is 4.0 cm2. The total volume of bulb
and stem is 16.8 cm2. When
immersed in water, the hydrometer
floats with 1.7 cm of the stem
above the water surface. In alcohol,
1.0 cm of the stem is above the
water surface. Find the density of
alcohol. II. Water stands to a height of 2.50 m
in a large tank which contains
compressed air maintained at an
absolute pressure of 1.100×105
N/m2. The horizontal outlet of the
pipe has crosssectional areas of
0.0300 m2 and 0.0100 m2 at the
larger and smaller sections. 1
3
2.5m
h
B 2 a) What is the velocity of the fluid as it leaves the outlet into the
atmosphere? b) What is the velocity of the fluid at the point B, as shown in
the figure? c) To what height h does water stand in the open ended pipe? Page 3 of 7 © Prep101 http://www.prep101.com/freestuff Problem 4
A simple harmonic oscillator, consisting of a mass, m, on a frictionless
horizontal surface connected to a spring, has a period of 0.8s and an
amplitude of 8.0cm.
a) Write an equation for displacement, x, as a cosine function of
time if at time t=0s the mass is at x=0.30cm from the
equilibrium position.
b) Draw a diagram of displacement as a function of time,
starting at time t=0 with a positive velocity.
c) It is found that a force of 5.0 N stretches the spring 3.0 cm
further than does a force of 3.0 N. Find the value of the mass
m.
d) Find an expression for the acceleration, a, in terms of the
angular velocity, ω, when the displacement is 4.0 cm.
e) At what displacement is the potential energy equal to the
kinetic energy? Page 4 of 7 © Prep101 http://www.prep101.com/freestuff Problem 5
I. The graph shows a plot at t=0.50s of the displacement of a 3.0 Hz
wave traveling in the –x direction along a string. 8.00 B 6.00
4.00
2.00 D (cm) A 0.00
0.05 0.10 0.15 0.20 0.25 2.00
4.00
6.00
8.00 x (m) a) What is the speed of the wave?
b) Write an equation describing the wave with all the constants
evaluated.
c) What is the transverse speed of the string a t=0.10s for
points A and B?
d) On the graph, sketch the displacement at t=0.
e) Write the equation of the wave that, when added, will
produce a standing wave.
II. A jet plane emits 8.0×105 J of sound energy per second.
a) What is the sound level in decibels 40.0m away?
b) Air absorbs sound at a rate of 7.0 dB/km. What will the sound
level 1.5 km away from the plane be, taking into account air
absorption? Page 5 of 7 © Prep101 http://www.prep101.com/freestuff Page 6 of 7 © Prep101 http://www.prep101.com/freestuff Problem 6
a) A steel tape measure gives the length of a brass rod to be 300.00
cm when both the tape measure and the rod are at 25°C. What would
the tape measure read when both are at 60°C?
[αbrass=19×106 K1 ; αsteel=11×106 K1 ]
b) The average rate at which heat flows through Mars’ surface is 70
W/m2 and the average thermal conductivity of Mars’ crust is k=4.1
W/m/K.
What is the temperature at the base of the crust if its thickness is
20km and the surface temperature is 210°C?
c) How long would it take in space to turn a 1.4 kg sphere of water
with surface area 0.06 m2 into ice in an environment with temperature
Text=5K? (assume ε=1.0, Lsol_w=3.33 and that the sphere is “floating”
in space) Page 7 of 7 ...
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This note was uploaded on 01/06/2011 for the course PHYS 101 taught by Professor Bates during the Fall '08 term at UBC.
 Fall '08
 BATES
 Physics

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