A 4.2-kg object, initially at rest, "explodes" into three objects of equal mass. Two of these are determined to have velocities of equal magnitudes (5.0 m/s) with directions that differ by 90°. How much kinetic energy was released in the explosion?
a. 70 J
b. 53 J
c. 60 J
d. 64 J
e. 35 J
a
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Compared to a bar of pure gold, the density of a pure gold ring is
A) less. B) the same. C) slightly more. D) much more.
The mass of a body on the moon is _______________ the mass of the same body on earth
Fill in the blank(s) with correct word
During one day and night in the mid-northern hemisphere, the stars near the north celestial pole
a. rise in the east. b. set in the west. c. circle the north celestial pole counter-clockwise. d. circle the north celestial pole clockwise.
Suppose an engineer suggests that air instead of water could flow through the tube and the velocity of the air could be increased until the heat transfer coefficient with the air equals that obtained with water at 1.5 m/s. Determine the velocity required and comment on the feasibility of the engineer’s suggestion. Note that the speed of sound in air at 100°C is 387 m/s.
GIVEN
• Air flow through a tube
• Bulk inlet air temperature (Tb,in) = 93°C
• Tube diameter (D) = 0.015 m
• Tube length (L) = 0.3 m
• Tube surface temperature (Ts) = 204°C
• From Problem 7.32: h ,c L = 13,037 W/(m2 K)
FIND
• The velocity (V) required to obtain h ,c L = 13,037 W/(m2 K)
ASSUMPTIONS
• Steady state
• Constant and uniform tube temperature
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the inlet bulk temperature of 93°C
Thermal conductivity (k) = 0.0302 W/(m K)
Kinematic viscosity (?) = 22.9 × 10–6 m2/s
Prandtl number (Pr) = 0.71