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Unformatted text preview: tal depth of the tank L. You can treat the device as an infinite parallel plate capacitor.
a)
b)
c)
d)
e) Deff = (Dfuel 1)(h/L)+1
Deff = Dfuel (h/L)
Deff = (1Dfuel)(h/L)
Deff = Dfuel(L/h)+1
Deff = Dfuel (L/h) Air
L Fuel h End view of the
picture above 5: (5 points) Consider the following five wave functions. Which of these travels to the right with
the largest velocity?
a)
b)
c)
d)
e) y = 10 cos(3x – 4t)
y = 10 cos(5x + 4t)
y = 20 cos(10x  60t)
y = 20 cos(4x + 20t)
y = 30 cos(12x – 12t) The units for amplitudes, wave numbers, and angular frequencies are the same for all five of
these. 6: (5 points) Two sources emit sound waves with a wavelength of 2 cm which travel out from
them in every direction. The sources are 3 cm apart, and oscillate in phase with one another (so
that each releases peaks at the same moment). If each source emits waves with intensity I0,
what is the total wave intensity at point 4 cm directly below one of the sources?
3 cm
a.
b.
c.
d.
e. 2I0
21/2I0
4I0/5
31/2I0/2
Zero 4 cm 7: (5 points) A typical neuronal axon has a diameter of 5 µm and is 10 cm long. When an
action potential is fired, the peak current in the axon is roughly 1x1010 Amps. What is the
peak magnetic force that each axon exerts on another when they run in parallel (just
touching each other) and fire synchronously, carrying currents in the same direction?
a)
b)
c)
d)
e) zero – there is no net force
4 x 1012 N, attractive
4 x 1012 N, repulsive
4 x 1023 N, attractive
4 x 1023 N, repulsive 8: (5 points) A neutron has no net charge, but nonetheless a magnetic moment with a zcomponent of 9.66 x 1027 A m2. This can be explained by the internal structure of the
neutron: two “down quarks” with a charge of –qe/3, and one “up quark” with charge +2qe/3.
In a simple model, the down quarks (labeled d) move clockwise, and the up quark (labeled
u) counterclockwise with the same velocity in a circle that corresponds to the size of the
neutron, with radius r = 1.2 x 1015 m. With roughly what velocity do the quarks have to orb...
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 Spring '08
 Mckay
 Physics

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