The weight of a car of mass 1.20 × 103 kg is supported equally by the four tires, which are inflated to the same gauge pressure
What gauge pressure in the tires is required so the area of contact of each tire with the road is 1.00 × 102 cm2? (1 atm = 1.01 × 105 Pa.)
A) 2.94 × 105 Pa
B) 2.94 × 103 Pa
C) 11.6 × 104 Pa
D) 2.94 × 104 Pa
E) 11.6 × 105 Pa
A
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The heat loss from uninsulated hot water pipes installed in homes can be considerable and hence increases the overall energy cost of the home. Consider a 5-m-long section of such a pipe that has an outer diameter of 1.7 cm and a surface temperature of 75°C. If the room air temperature is 20°C, calculate the natural convection heat loss from the pipe section. If the radiation heat losses are to be included as well, determine its contribution as a percentage of the total pipe heat transfer rate; assume that the outer pipe surface has an emissivity of 0.7.
GIVEN
• Uninsulated hot water pipe dissipating heat to surrounding
• Emissivity (?) = 0.7
• Diameter of cylinder (D) = 1.7 cm= 0.017 m
• Surface temperature (Ts) = 75°C= 348 K
• Ambient air temperature (T?) = 20°C= 293 K
• Length of the cylinder (L)= 5 m
FIND
(a) Natural convection heat loss from pipe section.
(b) Contribution of radiation as percentage of
total pipe heat transfer rate.
SKETCH
ASSUMPTIONS
• Air is still
• Surface temperature is uniform and constant
PROPERTIES AND CONSTANTS
for dry air at the mean temperature of 47.5°C
Thermal expansion coefficient (?) = 0.00312 1/K
Thermal conductivity (k) = 0.02695 W/(m K)
Kinematic viscosity (?) = 18.27 × 10–6 m2/s
Prandtl number (Pr) = 0.71
The mass of 6 million atoms of a diatomic gas is 
What is the atomic mass of this gas?
A. 25.5 u B. 51.0 u C. 2.55 u D. 5.10 u
A valve is closed and the fluid within a pipe is stationary. When the valve is opened, fluid flows through the pipe. What happens to the pressure in the pipe when the valve is opened?
A) The direction of the pressure change depends on the direction of the fluid flow. B) The direction of the pressure change depends on the density of the fluid. C) The pressure decreases. D) The pressure increases. E) The pressure remains the same.
Metric System: The volume of a 10-mL test tube is equivalent to which one of the following quantities?
A. 0.01 L B. 0.001 kL C. 0.1 L D. 1 × 10-6 L E. 0.001 ML