(a) The density of water at 0 ° C is very nearly 1 000 kg / m 3 (it is actually 999 . 84 kg / m 3 ), whereas the density of ice at 0 ° C is 917 kg / m 3 . Calculate the pressure necessary to keep ice from expanding when it freezes, neglecting the effect such a large pressure would have on the freezing temperature. (This problem gives you only an indication of how large the forces associated with freezing water might be.) (b) What are the implications of this result for biological cells that are frozen?
(a) The density of water at 0 ° C is very nearly 1 000 kg / m 3 (it is actually 999 . 84 kg / m 3 ), whereas the density of ice at 0 ° C is 917 kg / m 3 . Calculate the pressure necessary to keep ice from expanding when it freezes, neglecting the effect such a large pressure would have on the freezing temperature. (This problem gives you only an indication of how large the forces associated with freezing water might be.) (b) What are the implications of this result for biological cells that are frozen?
0
°
C
is very nearly
1
000
kg
/
m
3
(it is actually
999
.
84 kg
/
m
3
), whereas the density of ice at
0
°
C
is
917 kg
/
m
3
. Calculate the pressure necessary to keep ice from expanding when it freezes, neglecting the effect such a large pressure would have on the freezing temperature. (This problem gives you only an indication of how large the forces associated with freezing water might be.) (b) What are the implications of this result for biological cells that are frozen?
Helicobacter pylori (H. pylori) is a helically-shaped bacterium that is usually found in the stomach. It burrows through the gastric mucous
lining to establish an infection in the stomach's epithelial cells (see photo). Approximately 90% of the people infected with H. pylori will
never experience symptoms. Others may develop peptic ulcers and show symptoms of chronic gastritis. The method of motility of H.
pylori is a prokaryotic flagellum attached to the back of the bacterium that rigidly rotates like a propeller on a ship. The flagellum is
composed of proteins and is approximately 40.0 nm in diameter and can reach rotation speeds as high as 1.50 x 103 rpm. If the speed
of the bacterium is 10.0 μm/s, how far has it moved in the time it takes the flagellum to rotate through an angular displacement of 5.00
* 10² rad?
Zina Deretsky, National Science
Foundation/Flickr
H. PYLORI CROSSING MUCUS LAYER OF STOMACH
H.pylori Gastric Epithelial
mucin cells
gel
Number
i
318
Units
um
H.pylori…
T1. Calculate what is the received frequency when the car drives away from the radar antenna at a speed v of a) 1 m/s ( = 3.6 km/h), b) 10 m/s ( = 36 km/h), c) 30 m /s ( = 108 km/h) . The radar transmission frequency f is 24.125 GHz = 24.125*10^9 Hz, about 24 GHz. Speed of light 2.998 *10^8 m/s.
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
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