Consider an electrically heated brick house ( k = 0 .40 Btu/h .ft°F ) and whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varies. On a certain day, the temperature of the inner surface of the walls is measured to be at 55°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h. Determine the amount of heat lost from the house that day. Also determine the cost of that heat loss to the homeowner for an electricity price of $0.09 kWh.
Consider an electrically heated brick house ( k = 0 .40 Btu/h .ft°F ) and whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varies. On a certain day, the temperature of the inner surface of the walls is measured to be at 55°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h. Determine the amount of heat lost from the house that day. Also determine the cost of that heat loss to the homeowner for an electricity price of $0.09 kWh.
Solution Summary: The author calculates the amount of heat loss from the house on the day and also calculate the cost of that heat.
Consider an electrically heated brick house
(
k
=
0
.40 Btu/h
.ft°F
)
and whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varies. On a certain day, the temperature of the inner surface of the walls is measured to be at 55°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h. Determine the amount of heat lost from the house that day. Also determine the cost of that heat loss to the homeowner for an electricity price of $0.09 kWh.
8. All of the members in the Warren truss of Figure 8 are of length 10 ft. Use the method of
sections to determine the forces in the members BD,CD,CE.
B
A
C
D
E
F
G
2000 lb
3000 lb
5000 lb
Figure 8
H
An acrobat is walking on a tightrope of length L
=20.1 m attached to supports A and B at a
distance of 20.0 m apart. The combined weight
of the acrobat and his balancing pole is 900 N,
and the friction between his shoes and the rope
is large enough to prevent him from slipping.
Neglecting the weight of the rope and any
elastic deformation, determine the deflection (y)
and the tension in portion AC and BC of the
rope for values of x from 0.5 m to 10 m using
0.5 m increments.
1. Determine the maximum deflection (y) in
the rope.
2. Plot tension of AC and BC vs. x (on the
same plot with x on the x-axis). Turn in the
plot and the table of x, TAC, and TBC (clearly
label each).
A
C
20.0 m
B
5. A 4000 lb block of concrete is attached by light inextensible cables to the truss in Figure 5.
Determine the force in each member. State whether each member is in tension or compression.
3
ΘΑ
D
E
cables
all dimensions in feet.
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