A thin spherical shell of radius 20.0 cm has 5.0 ?C of charge uniformly distributed over its surface. What is the magnitude of the electric field 2.00 m from the center of the sphere?
a. 
b. 
c. 
d. 
e. 0
e. 0
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The position of a particle moving along the x axis is given by x = 6.0t2? 1.0t3, where x is in meters and t in seconds. What is the position of the particle when it achieves its maximum speed in the positive x direction?
A. 24 m B. 12 m C. 32 m D. 16 m E. 2.0 m
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
If atmospheric pressure increases by an amount ?p, which of the following statements about the pressure in a lake is true? (There could be more than one correct choice.)
A) The absolute (total) pressure does not change. B) The gauge pressure increases by ?p. C) The absolute (total) pressure increases by ?p. D) The absolute (total) pressure increases, but by an amount less than ?p. E) The gauge pressure does not change.
Our home galaxy is called _______________
a. M31 b. the solar system c. the Milky Way d. Andromeda