A skater rotates quickly on the ice. He pushes his arms out. What happens to his rotational kinetic energy?
1.It increases.
2.It decreases.
3.It stays the same.
4.It is impossible to determine.
2
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Index of Refraction: Light having a frequency in vacuum of 6.0 × 1014 Hz enters a liquid of refractive index 2.0. What is the frequency of the light in this liquid? (c = 3.0 × 108 m/s)
A. 12 × 1014 Hz B. 6.0 × 1014 Hz C. 3.0 × 1014 Hz D. 1.5 × 1014 Hz E. 2.0 × 1014 Hz
Which of the following type of electromagnetic radiation has the lowest energy?
A) radio B) infrared C) visible D) ultraviolet E) X-ray
Develop an expression for the ratio of the rate of heat transfer to water at 40°C from a thin flat strip of width ?D/2 and length L at zero angle of attack and a tube of the same length and diameter D in cross-flow with its axis normal to the water flow in the Reynolds number range between 50 and 1000. Assume both surfaces are at 90°C.
GIVEN
• Water flowing over a thin flat strip at zero angle of attack or a tube in crossflow
• Water temperature (T?) = 40°C
• Tube diameter = D
• Strip width = ?D/2
• Tube and strip length = L
• Reynolds number: 50 < Re < 1000
FIND
• The ratio of the heat transfer from the strip and that from the cylinder. (qs/qt)
ASSUMPTIONS
• Steady state for both cases
• The tube and strip temperatures (Ts) are 90°C SKETCH
PROPERTIES AND CONSTANTS
for water at 40°C: Prandtl number (Pr) = 4.3 At the surface temperature of 90°C: Prs = 1.94
SKETCH
Some double-pane airplane windows darken when the inner pane is rotated. The panes are
A) thin films. B) Polaroid filters. C) optical fibers.