Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle. Consider a 100-mm-thick plate k = 45 W / m ⋅ K , ρ = 7800 k g / m 3 , c p = 500 J / k g ⋅ K that is initially at a uniform temperature of 300°C and is heated (on both sides) in a gas-fired furnace for which T ∞ = 700 ° C and h = 500 W / m 2 ⋅ K . How long will it take for a minimum temperature of 550°C to be reached in the plate?
Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle. Consider a 100-mm-thick plate k = 45 W / m ⋅ K , ρ = 7800 k g / m 3 , c p = 500 J / k g ⋅ K that is initially at a uniform temperature of 300°C and is heated (on both sides) in a gas-fired furnace for which T ∞ = 700 ° C and h = 500 W / m 2 ⋅ K . How long will it take for a minimum temperature of 550°C to be reached in the plate?
Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle. Consider a 100-mm-thick plate
k
=
45
W
/
m
⋅
K
,
ρ
=
7800
k
g
/
m
3
,
c
p
=
500
J
/
k
g
⋅
K
that is initially at a uniform temperature of 300°C and is heated (on both sides) in a gas-fired furnace for which
T
∞
=
700
°
C
and
h
=
500
W
/
m
2
⋅
K
. How long will it take for a minimum temperature of 550°C to be reached in the plate?
A piston-cylinder device contains 0.87 kg of refrigerant-134a at -10°C. The piston that is free to move has a mass of 12 kg
and a diameter of 25 cm. The local atmospheric pressure is 88 kPa. Now, heat is transferred to refrigerant-134a until the
temperature is 15°C. Use data from the tables.
R-134a
-10°C
Determine the final pressure of the refrigerant-134a.
The final pressure is
kPa.
The hydraulic cylinder BC exerts on member AB a force P directed along line BC. The force P must have a 560-N
component perpendicular to member AB.
A
M
45°
30°
C
Determine the force component along line AB.
The force component along line AB is
N.
!
Required information
A telephone cable is clamped at A to the pole AB. The tension in the left-hand portion of the cable is given to be
T₁ = 815 lb.
A
15°
25°
B
T₂
Using trigonometry, determine the required tension T₂ in the right-hand portion if the resultant R of the forces exerted by the cable at
A is to be vertical.
The required tension is
lb.
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