Two wheels have the same total mass M and radius R. One wheel is a uniform disk. The other is like a bicycle wheel, with lightweight spokes connecting the rim to a small hub. Which likely has the larger moment of inertia?
A. The solid disk.
B. The wheel with spokes.
C. The moment of inertia will be nearly the same for both.
D. We need more information to answer.
B. The wheel with spokes.
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A spaceship is headed toward Alpha Centauri at 0.999c. According to us, the distance to Alpha Centauri is about 4 light-years. How far away is Alpha Centauri according to the travelers in the ship?
A) also about 4 light-years B) very slightly more than 4 light-years C) very slightly less than 4 light-years D) quite a bit less than 4 light-years E) quite a bit more than 4 light-years
The buoyant force that acts on a 10-ton ship floating in the ocean is
A) less than 10 tons. B) 10 tons. C) greater than 10 tons. D) depends on the density of seawater
Your vocal cords are used to produce all the sounds you make while speaking
a. True b. False Indicate whether the statement is true or false
A journal bearing has a clearance of 0.5 mm. The journal has a diameter of 100 mm and rotates at 3600 rpm within the bearing. The journal is lubricated by an oil having a density of 800 kg/m3 , a viscosity of 0.01 kg/(ms), and a thermal conductivity of 0.14 W/(m K). Both the journal and the bearing temperatures are maintained at 60°C. Calculate the rate of heat transfer from the bearing and the power required for rotation per unit length.
GIVEN
A journal bearing
Diameter (D) = 100 mm = 0.1 m
Clearance (H) = 0.5 mm = 0.0005 m
Rotational speed (@) = 3600 rpm
Oil properties
? Density (p) = 800 kg/m3
? Viscosity (?) = 0.01 kg/(ms)
? Thermal conductivity (k) = 0.14 W/(m K)
Temperature of both surface (Tb) = 60°C
FIND
(a) The rate of heat transfer from the bearing
(b) The power required for rotation per unit length
ASSUMPTIONS
Steady state
Uniform and constant surface temperatures
Constant fluid properties
SKETCH
