After the first solid grains formed in our solar system, these particles could then grow by the process of ____________, the collision and sticking of one particle with another to continue the formation of planetesimals. Each of these has many atoms or molecules
a. accretion
b. sublimation
c. hydration
d. condensation
e. vaporization
a
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A moving object’s length in a given frame is defined to be the distance between two events that occur at opposite ends of the object and that are simultaneous in that frame. Why is it crucial that the events we use to define a moving object’s length be simultaneous?
A. This is purely conventional: there is no other reason. B. This choice makes it easier to use the Lorentz transformation equations to find the length. C. If the events are not constrained to be simultaneous, then the length is poorly defined: its value would depend on the time interval between the events. D. If the events are simultaneous, then the length will be a frame-independent quantity. E. Other (specify)
The person who first explained the photoelectric effect was __________
Fill in the blank(s) with correct word
Upper-main-sequence stars, more massive than the Sun, fuse hydrogen by the proton-proton chain
Indicate whether the statement is true or false
A heat exchanger wall consists of a copper plate 2 cm thick. The heat transfer coefficients on the two sides of the plate are 2700 and 7000 W/( m2 K), corresponding to fluid temperatures of 92 and 32°C, respectively. Assuming that the thermal conductivity of the wall is 375 W/ ( m K), (a) compute the surface temperatures in °C, and (b) calculate the heat flux in W/ m2.
GIVEN
• Heat exchanger wall, thickness (L) = 2 cm = 0.02 m
• Heat transfer coefficients
? hc1 = 2700 W/(m2 K)
? hc2 = 7000 W/(m2 K)
• Fluid temperatures
? Tf1 = 92°C
? Tf2 = 32°C
• Thermal conductivity of the wall (k) = 375 W/( m K) FIND (a) Surface temperatures (Tw1, Tw1) in °F (b) The heat flux (q/A) in W/m2. ASSUMPTIONS
• One dimensional heat transfer prevails
• The system has reached steady state
• Radiative heat transfer is negligible
SKETCH
