A beam of electrons moves at velocity
. The number of particles per unit volume in the beam of area
A is
. If we imagine a cylindrical Gaussian surface of radius
r and length
centered on the beam, the electron flux through the surface is
a.
0.
b.
vf A.
c.
2
vf A.
d.
vf (
A+2
r).
e.
2vf (
A+
r).
Question 2Gino says that the analog of Gauss's law for the flow of an incompressible fluid of density
at constant velocity
is
for an imaginary surface within the fluid. Lorenzo says that it is true only if the area where the fluid enters the surface and the area where it leaves the surface are both perpendicular to the velocity of the fluid. Which one, if either, is correct?
a.
Gino, because as much fluid leaves as enters.
b.
Lorenzo, because
is not equal to zero if the fluid enters or exits at angles other than 90.
c.
Lorenzo, because this is true only when the fluid executes rotational motion.
d.
Gino, because it is true only when the fluid is enclosed on all sides, not when it is flowing.
e.
Lorenzo, because it is true only when the fluid is enclosed on all sides, not when it is flowing.
Pulmonary function test: spirometry. (a) Normal respiratory volumes, as measured during spirometry.
Illustration of the Brain Lobes Showing Location of Broca’s Area and Wernicke’s Area
Schematic of Rectification Unit
The inguinal area. Take great care when applying deep pressure in this region
Average Number of Days per Year with Thunderstorms
Trigonometry, Area Problem