Download sample unit#2 exam - BYU Physics and Astronomy

SAMPLE UNIT#2 EXAM KEY
1. Suppose the temperature is 65°F (saturation vapor pressure at 65°F is 21.0 mb) and the dew point
is 50°F (saturation vapor pressure at 50°F is 12.3 mb). The relative humidity is (a) 29%, (b) 38%,
(c) 45%, (d) 59%, (e) 77%, (f) 100%.
2. On four consecutive summer days the mid-afternoon temperature is 95°F. However on the first
day the wet-bulb temperature is 72°F; on the second, 75°F; on the third, 81°F; and on the fourth,
76°F. Which day is most comfortable for an out-of-doors worker? The (a) first, (b) second, (c)
third, (d) fourth.
3. A cloud consisting of condensation along the trail of a jet aircraft is known as a (a) banner cloud,
(b) contrail, (c) jet stream, (d) lenticular cloud, (e) pileus cloud.
4. On a morning when the temperature is 40°F the relative humidity is 60%. Later in the day the
temperature reaches 60°F. If the saturation vapor pressure is 8.4 mb at 40°F and 17.7 mb at 60°F,
what is the relative humidity when the temperature reaches 60°F? (Assume that the same air
mass remains over the area during the day.) (a) 7%, (b) 28%, (c) 47%, (d) 79%.
5. The principal reason that blizzards hardly ever occur in Provo is that (a) there is usually
insufficient snowfall, (b) temperatures are rarely cold enough, (c) local snow here is generally too
wet to be blown about much by the wind, (d) the local topography is such that strong winds
seldom occur during and after snowfall.
6. Which of the following processes leads to a cooling of the environment? (a) condensation, (b)
deposition, (c) freezing, (d) sublimation.
7. Raindrops rarely exceed a maximum diameter of about 5 millimeters. This is so because (a)
raindrops larger than this are unstable and break into fragments, (b) the time required for
raindrops to fall from a cloud top to the ground is never long enough for drops to grow larger than
about this size, (c) drops larger than this size are held aloft by updrafts, (d) drops larger than this
size are held aloft by buoyant forces, (e) drops larger than this size were prohibited by an act of
congress during the F.D. Roosevelt administration.
8. Precipitation is falling from altostratus clouds on a day when the surface temperature is 24°F and
a strong, deep temperature inversion extends from the surface to 2500 feet above the surface
where the temperature is 37°F. Above that the temperature profile is close to the standard lapse
rate. The surface precipitation is most likely (a) hail, (b) freezing rain, (c) sleet, (d) snow, (e)
oobleck.
9. The sum of all forces exerted on a certain stationary object by its environment is zero. If that
object is slightly displaced from its initial position its environment exerts a net force on it which
tends to move it back towards its initial position. The system is in a state of (a) neutral
equilibrium, (b) non-equilibrium, (c) stable equilibrium, (d) unstable equilibrium.
10. The base of a cumulus cloud is 1500 meters above the surface at a level where the temperature is
14°C. What is the dew point at an altitude 3000 meters above the surface and within the cloud?
(a) -1°C, (b) 2°C, (c) 5°C, (d) 11°C, (e) 14°C.
11. Based on the standard lapse rate, the standard atmosphere is (a) absolutely stable, (b) absolutely
unstable, (c) conditionally unstable, (d) none of the preceding.
12. Any rising air parcel tends to (a) expand and cool, (b) expand and warm up, (c) contract and cool,
(d) contract and warm up, (e) do any of the above, or not change at all, depending on the
environmental lapse rate, (f) either (a) or (b) depending on the environmental lapse rate.
13. The sky is covered by tightly packed, small, puffy, almost uniformly white clouds. Those cloud
puffs high above the horizon each subtend an angle about like the angle subtended by one's little
fingernail viewed with one's arm extended. The cloud type is (a) altocumulus, (b) altostratus, (c)
cirrocumulus, (d) cirrostratus, (e) cirrus, (f) cumulonimbus, (g) cumulus, (h) nimbostratus, (i)
stratocumulus, (j) stratus.
14. Which of the following measures of atmospheric moisture expresses the mass of atmospheric
water vapor per unit volume of air? (a) absolute humidity, (b) actual vapor pressure, (c) mixing
ratio, (d) relative humidity, (e) saturation vapor pressure, (f) specific humidity.
15. A 27°F air mass settles over the Great Salt Lake. Steam fog will most likely form if the season is
(a) late fall, (b) early winter, (c) late winter, (d) early spring, (e) season makes no difference.
16. On a fall day when the atmospheric temperature gradient matches the standard lapse rate the
temperature on the BYU campus (elevation = 4600 feet) is 59°F. What is the is the approximate
temperature at the same time on the summit of Timpanogos (elevation = 11750 feet)? (a) 20°F,
(b) 33°F, (c) 37°F, (d) 44°F, (e) 52°F.
17. Which of the following conditions does not promote atmospheric stability? (a) Nighttime
radiative surface cooling, (b) cold advection at the surface, (c) cold advection aloft, (d)
subsidence, (e) warmer air moving over a cold surface.
18. The figure at the right shows
the relationship between the
temperature (top) and some
other atmospheric variable for
a 24-hour period during
October, 2009. The second
variable plotted is the
atmospheric (a) pressure, (b)
relative humidity, (c) wind
speed, (d) degree of cloud cover.
19. The famous fogs of the San Francisco Bay area are mainly of which type? (a) advection fog, (b)
frontal fog, (c) radiation fog, (d) steam fog, (e) upslope fog.
20. Orographic uplift is occurring along the western slope of a 2500-meter high mountain. At the
western base of the mountains the temperature is 25°C (77°F) and the dew point is 17°C (62.6°F).
At the summit of the mountain the temperature is (a) 0°C (32°F), (b) 3°C (41°F), (c) 6°C
(42.8°F), (d) 10°C (50°F), (e) 12°C (53.6°F).