A 9-cm-diameter potato ( p = 1100 kg/m 3 , cp = 3900 J/kg .K, k = 0 .6 W/m .K, α = 1 .4 × 10 -7 m 2 /s) and that is initially at a uniform temperature of 25°C is baked in an oven at 170°C until a temperature sensor inserted into the center of the potato indicates a reading of 70°C. The potato is then taken out of the oven and wrapped in thick towels so that almost no heat is lost from the baked potato. Assuming the heat transfer coefficient in the oven to be 40 W/m 2 K, determine (a) how long the potato is baked in the oven and (b) the final equilibrium temperature of the potato after it is wrapped. Solve this problem using the analytical one-term approximation method.
A 9-cm-diameter potato ( p = 1100 kg/m 3 , cp = 3900 J/kg .K, k = 0 .6 W/m .K, α = 1 .4 × 10 -7 m 2 /s) and that is initially at a uniform temperature of 25°C is baked in an oven at 170°C until a temperature sensor inserted into the center of the potato indicates a reading of 70°C. The potato is then taken out of the oven and wrapped in thick towels so that almost no heat is lost from the baked potato. Assuming the heat transfer coefficient in the oven to be 40 W/m 2 K, determine (a) how long the potato is baked in the oven and (b) the final equilibrium temperature of the potato after it is wrapped. Solve this problem using the analytical one-term approximation method.
A 9-cm-diameter potato
(
p
=
1100
kg/m
3
, cp = 3900 J/kg
.K, k = 0
.6 W/m
.K,
α
= 1
.4
×
10
-7
m
2
/s)
and that is initially at a uniform temperature of 25°C is baked in an oven at 170°C until a temperature sensor inserted into the center of the potato indicates a reading of 70°C. The potato is then taken out of the oven and wrapped in thick towels so that almost no heat is lost from the baked potato. Assuming the heat transfer coefficient in the oven to be 40 W/m2 K, determine (a) how long the potato is baked in the oven and (b) the final equilibrium temperature of the potato after it is wrapped. Solve this problem using the analytical one-term approximation method.
The 120 kg wheel has a radius of gyration of 0.7 m. A force P with a magnitude of 50 N is applied at the edge of the wheel as seen in the diagram. The coefficient of static friction is 0.3, and the coefficient of kinetic friction is 0.25. Find the acceleration and angular acceleration of the wheel.
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Using MATLAB , find the magnitude and phase plot of the compensators
NO COPIED SOLUTIONS
4-81 The corner shown in Figure P4-81 is initially uniform at 300°C and then suddenly
exposed to a convection environment at 50°C with h 60 W/m². °C. Assume the
=
2
solid has the properties of fireclay brick. Examine nodes 1, 2, 3, 4, and 5 and deter-
mine the maximum time increment which may be used for a transient numerical
calculation.
Figure P4-81
1
2
3
4
1 cm
5
6
1 cm
2 cm
h, T
+
2 cm
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