Potential: A proton that is initially at rest is accelerated through an electric potential difference of magnitude 500 V. What speed does the proton gain? (e = 1.60 × 10-19 C , mproton = 1.67 × 10-27 kg)
A. 2.2 × 105 m/s
B. 3.1 × 105 m/s
C. 9.6 × 105 m/s
D. 1.1 × 105 m/s
Answer: B
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In a spectroscopic binary, if a pair shows a combined set of lines tonight, but a maximum split two nights later, its orbital period must be
A) one day. B) two days. C) four days. D) eight days. E) twelve days.
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
Which statement correctly describes the role of dark matter in galaxy formation?
A) Where baryons collect, dark matter follows. B) Dark matter plays very little role in galaxy formation. C) Where dark matter collects, the baryons follow.
Light bulb A is rated at 60 W and light bulb B is rated at 100 W. Both are designed to operate at 110 V. Which statement is correct?
a. The 60 W bulb has a greater resistance and greater current than the 100 W bulb. b. The 60 W bulb has a greater resistance and smaller current than the 100 W bulb. c. The 60 W bulb has a smaller resistance and smaller current than the 100 W bulb. d. The 60 W bulb has a smaller resistance and greater current than the 100 W bulb. e. We need to know the resistivities of the filaments to answer this question.