USEFUL CONSTANTS for WATER: c = 4186 J/kg AoC
= 1.00 cal/gm A oC ,
Lf = 3.33x105 J/kg = 79.7 cal/gm
Lv = 2.26x106 J/kg = 540 cal/gm
ICE: c = 2090 J/kg A oC
= 0.500 cal/gm A oC
STEAM: c = 2010 J/kg AoC
= 0.480 cal/gm A oC
pressure: 1.00 atm = 1.01 x 105 N/m2
1] A semicircular area of radius 10.00 cm is cut
into
the side of a large flat piece of
steel at 20.00oC. What is the final total area of
the semicircle if the piece of steel is
heated to 200.0oC ? [ for steel, ( a
= 11.0 x 10-6 / oC ) ]
Answer: 157.6 cm2
2] What mass of ice that is initially at -15.0oC
is needed to cool 250 gm of water in a
150 gm glass container from 20.0oC down to 5.0oC
? [for glass, c = 0.20 cal/(g oC) ]
Answer: 45.6 gm
3] Suppose your skin has an emissivity of 0.70 and
that 0.27 m2 of bare skin is exposed to
the air which is at a temperature of 20oC. Assume
your skin is at a temperature of 37oC and
determine the net power radiated by this exposed area of skin.
Answer: 20 W
If the molecular mass of
oxygen is 32.0 gm/mole, what is the mass
of oxygen in the tank?
ANSW: 40 degrees Celsius
4] Air has a much lower thermal conductivity than
foam insulation. Why then do we put foam
insulation in the walls and ceilings of houses?
Answer: To prevent convection. It is
"dead" air spaces that are needed. In open wall and ceiling
spaces the air will convect heat from inner "warm"
walls to the outer "cold" walls.
MULTIPLE
CHOICE QUESTION
1) Studies of the expansion of metals show that different
metals
A) expand at different rates when heated
B) expand at different rates when cooled
C) expand at the same rates when heated
D) expand at the same rates when cooled
E) don't expand until a certain temperature is
reached