What are the short- and long-term effects of the Moon's tides on our rotation?
What will be an ideal response?
The Moon slows down our rotation slightly, with precession being the long-term effect of this tidal distortion.
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Water enters a double pipe heat-exchanger at 60°C. The water flows on the inside through a copper tube 2.54 cm ID at a velocity of 2 cm/s. Steam flows in the annulus and condenses on the outside of the copper tube at a temperature of 80°C. Calculate the outlet temperature of the water if the heat exchanger is 3-m-long.
GIVEN
• Water flow through a tube in a double pipe heat-exchanger
• Water entrance temperature (Tb,in.) = 60°C
• Inside tube diameter (D) = 2.54 cm = 0.0254 m
• Water velocity (V) = 2 cm/s = 0.02 m/s
• Steam condenses at (Ts) = 0.80°C on the outside of the pipe
• Length of heat exchanger (L) = 3 m
FIND
• Outlet temperature of the water (Tb,out)
ASSUMPTIONS
• Steady state
• Thermal resistance of the copper pipe is negligible
• Pressure in the annulus is uniform therefore, Ts is uniform
• Heat transfer coefficient of the condensing steam is large (see Table 1.4) so its thermal resistance can be neglected
• Outside surface of the heat exchanger is insulated
SKETCH
Consider an apple falling from a tree. Which of the following applies to this situation?
A. Earth is attracting the apple. B. The apple is attracting Earth. C. Earth is attracting the apple; the apple is not attracting Earth. D. The apple is attracting Earth and Earth is attracting the apple.
Describe how a simple electric cell works
What will be an ideal response?
A beam of X-rays of different frequencies is reflected at 10 degrees off a crystal of interatomic spacing 0.2 nm. Which X-ray wavelength is preferentially reflected?
a. 0.0943 nm b. 0.139 nm c. 0.0695 nm d. 1.02 × 10^?10 m e. 3.47 × 10^?11 m