A block of mass M slides down a frictionless plane inclined at an angle ? with the horizontal. The normal reaction force exerted by the plane on the block is
A) Mg.
B) Mg sin ?.
C) Mg cos ?.
D) Mg tan ?.
E) zero, since the plane is frictionless.
C
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A solar system contains
a. primarily planets. b. large amounts of gas and dust but very few stars. c. large amounts of gas, dust, and stars. d. a single star and planets. e. thousands of superclusters.
Calculate the maximum safe heat flux in the nucleate-boiling regime for water flowing at a velocity of 15 m/s through a 1.2-cm-ID tube 0.31-m-long if the water enters at 100 kPa pressure and 100°C saturated liquid.
GIVEN
? Nucleate boiling of water flowing through a tube
? Water velocity (V) = 15 m/s
? Tube inside diameter (D) = 1.2 cm = 0.012 m
? Tube length (L) = 0.31 m
? Water pressure (p) = 1 atm
? Water temperature (Tw) = 100°C
FIND
? The maximum safe heat flux in the nucleate boiling regime (q"max)
ASSUMPTIONS
? Steady state
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 13, for water at 100°C, 1 atm
From Appendix 2, Table 35, for steam at 100°C: pv = 0.5977 kg/m3
From Table 9.2: Surface tension at 100°C (s) = 0.0589 N/m
From Table 9.1: For water on copper, Csf = 0.0130
Which of the following statements is true?
A) a molecule is the smallest existing particle B) chemical elements are made up of about 100 distinct molecules C) molecules form atoms that determine chemical properties of a substance D) molecules are the smallest subdivision of matter that still retain a substance's chemical properties E) none of the above
Newton's Second Law of Motion tells us that the net force applied to an object equals its
A) mass times acceleration. B) mass times energy. C) momentum times velocity. D) mass times velocity.