PHYS 201 TEST #4 11/23/16
DR. HOLMES NAME

Do all eight problems. The
worth of each problem is marked beside the space for the answer. All answers
should be in MKS units unless otherwise indicated. Show your work for partial credit.
Work should be under the problem, or clearly labeled on an extra sheet placed
underneath the top page of the test.

1) a) If
you apply a force of 15 lbs on a cylinder of area
0.20 in^{2}, what is the gauge pressure on the fluid behind the
cylinder?

in lb/in^{2}: **75 lb/in ^{2}; **in Nt/m

b) If the fluid under the above pressure pushes
on another cylinder of area 18 in^{2}, what will be the force on this
cylinder?

in lbs: **1,350
lb.** in Nt: **6,014
Nt.**

2) a) What is the __gauge__
pressure at a depth of 900 feet (275 m) under water:?

in Nt/m²:
**2.70 x 10 ^{6} Nt/m^{2}** in lb/in²:

b) If you have a view plate on a submersible
that is 900 feet below the surface (and subject to the gauge pressure in
problem 2a above), what is the force due to this pressure on the view plate if
the area of the view plate is 500 cm^{2} (circular plate of diameter 10
inches)?

In Nt: **135,000 Nt**

In lbs:
**30,300 lb. ^{}**

** **

3) A small artery of inside
DIAMETER 0.62 mm and length 2.5 cm carries blood. Assume the beginning and the
end of the artery are at the same height.

a) If the pressure drop from
the front to the back of the artery is 4 mm Hg, what is the pressure drop
expressed in Nt/m^{2} ?

**532 Nt/m ^{2}**

b) Assuming there is the
above pressure drop, and given that the viscosity of the blood is 4 x 10^{-3}
Pl (about four times that of water), what is the volume flow of blood per time
through the artery (assume laminar flow) expressed:

in m^{3}/sec: **1.93
x 10 ^{-8} m^{3}/sec **

in cc/sec:** 0.0193 cc/sec**

c) Given that the density of
blood is 1.05 gm/cc, by how much would the blood pressure decrease due to
gravity by going up a distance of 32 cm (from the heart to the head)?

In Nt/m^{2}:**
3,293 Nt/m ^{2}**

In mm of Hg: **24.8 mm of
Hg.**

For problems 4 & 5,
consider a house 46 ft x 30 ft
x 8 ft with 1380 ft^{2} of floor (and
ceiling) space and an outside wall area of 1,216 ft^{2} (46 x 8 plus
30 x 8 plus 46 x 8 plus 30 x 8).

4) Assume the outside walls have thermal
insulation due to sheetrock and fiberglass with a total value of R = 15 ft^{2}*^{o}F*hr/BTU. Assume the average inside temperature is 68^{o}F
and the average outside temperature is 23^{o}F. Ignore other sources of heat loss such as
through the ceiling, through the floor, via convection and radiation.

a) What is the average heat loss per time (in

**1,040 Watts**

b) If the cost of energy is
$0.095 / kW*hr, what will the cost be for a month to
replace the energy lost by conduction?

**$71.12**

c) If the inside temperature is reset to 77^{o},
what will the new average heat loss per time (in

**1,248 Watts.**

5) For the house above (46 x 30 x 8):

a) What is the volume of air
space in this room?

in ft^{3} : **11,040 ft ^{3}; ** in m

Now assume the temperature in
the room is set to be 77^{o}F.

b) Calculate the number of
moles of air in this house:

**12,765 moles**

c) Is the number of moles of
air in the house when the temperature is 23^{o}F [more, the same, or
less] than when the temperature is 77^{o}F ?

**more.**

d) Given that the heat
capacity of air (at constant pressure) is (7/2)*R, how much energy would it
take to heat up the air in this house from 23°F to 77°F ?

**1.11 x 10 ^{7}
Joules = 3.09 kW-hr**

e) At $.095 / kW-hr, what
would this energy cost?

**$0.294 = 29.4 cents**

f) If the air in this house
is replace by outside air at the rate of once every 3 hours, how much would it
cost to keep this house heated for one month assuming the outside temperature
and inside temperature remained constant during the whole month and assuming
the outgoing hot air did not warm up the incoming cold air? (Neglect other sources of heat such as warm
bodies and losses due to radiation and conduction).

**$70.46**

6 a) How much energy does it
take to heat up 475 cc's of water (16 fluid ounces) (1 cc = 1 milliliter = 1 gram) from 77^{o}F
to boiling (212^{o}F) ?

**149,126 Joules = 35,625
calories**

b) How much energy does it
take to boil 475 cc's of water (if the water is already at 212^{o}F) ?

**1,073,700 Joules = 256,500
calories**

c) If a person burns energy
at the rate of 115 Watts, how much water (at 77^{o}) is needed each
hour to keep the person cool by evaporation (assume no heat is lost by
conduction or radiation ?

**161 cc/hr**.

7) Assume a certain person
has an average skin temperature of 92°F and a skin area of 0.84 m^{2}.

a) How much energy does this
person radiate per second (in

**419 Watts**

b) If the air temperature is
41°F, how much heat energy per time does this person receive from the air due
to radiation?

**284 Watts**

c) What is the net power lost
or gained by radiation by the person?

**135 Watts lost.**

8) a)
State the First Law of Thermodynamics:

b)
Where does this law come from, that is, is it a re-statement of a
previous law?

c)
State the Second Law of Thermodynamics

d)
Where does this law come from?: