The planet that most resembles Earth is ______________
Fill in the blank(s) with correct word
Mars
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Energy and Momentum: In a police ballistics test, a 2.00-g bullet suddenly hits and becomes embedded in a 5.00-kg wood block which is hanging from a 1.20-m long string. This causes the block to swing through an arc of 3.50°. What was the speed of the bullet just before it hit the block?
A. 16.7 m/s B. 524 m/s C. 25.3 m/s D. 262 m/s E. 789 m/s
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
The energy level diagram for hydrogen
The smallest energy of an absorbed photon that will raise a hydrogen atom from its ground state to its first excited state is
a.
1.5 eV.
b.
1.9 eV.
c.
3.4 eV.
d.
10.2 eV.
e.
13.6 eV.
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light. B) A refracting telescope produces refracted images while a reflecting telescope produces reflected images. C) Reflecting telescopes make much clearer images than can refracting telescopes of the same size. D) It is much easier to make a large refracting telescope than a large reflecting telescope.