Яндекс.Метрика

Saturday, March 28, 2015

Quiz 1 Key

1.  The measured length of a cylindrical laser beam is 12.1 meters, its measured diameter is 0.00121 meters, and its measured intensity is 1.21 ´ 105 W/m2. Which of these measurements is the most precise?  
A.  length
B.  diameter
C.  intensity
D.  All three are equally precise.

2.  Vectors A and B have the same non-zero magnitude. The magnitude of A + B is equal to the magnitude of A - B . What is the angle between  and B ? 
A. 30 degrees
B. 45 degrees
C. 60 degrees
D. 90 degrees
3. How many significant figures are in the number 0.00640? 
A. 1
B. 2
C. 3
D. 4
E. 5
4. A vector  A with magnitude 25.0 m points along the positive y direction. If it is rotated by 50.0 degrees counterclockwise, what are the components of the vector? 
A. Ax = 25.0 cos 50.0° and Ay = 25.0 sin 50.0°
B. Ax = 25.0 cos 140° and Ay = 25.0 sin 140°
C. Ax = 25.0 sin 140° and Ay = 25.0 cos 140°
D. Ax = 25.0 tan 50.0° and Ay = 25.0 sin 50.0°
E. All solutions above are wrong.
5. Assume that the mass of any cell in the human body is 5 ´ 10-15 kg. If Alice has a mass of 50 kg how many cells are there in her body? 
A. 1017 cells
B. 1016 cells
C. 1015 cells
D. 1014 cells
E. 1013 cells
6.  The answer with the correct number of significant figures to the following calculation: 1.345 ´ 6.72 + 4.51 is  
A.  13.5484.
B.  13.548.
C.  13.55.
D.  13.6.
E.  14
7.  If vector  and vector  , where  and  are the units vectors along the x and the y directions respectively, calculate the magnitude of vector  .  
A.  10.3
B.  17.4
C.  -6.7
D.  26
E.  -12.3
8.  The fraction of a cubic kilometer in a cubic millimeter is  
A.  10-18.
B.  10-12.
C.  10-9.
D.  10-6.
9. A cube with a volume of V consists of 6 faces each with an area of A. If the area of each face is increased by a factor of 64, by what factor does the volume increase? 
A. 8
B. 64
C. 384
D. 512
E. 4096
10.  Vector A points along the y axis with length 5.0, vector B makes an angle of 55° with respect to the x-axis and has a length of 7.0. What is the length of vector A - B?
     
A.  4.1
B.  12.
C.  2.0
D.  35.
E.  9.9

Friday, March 27, 2015

Chatting With ESA Scientist Jan Tauber, Mars Marathon, and Golden Sewage

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Q&A With ESA's Jan Tauber on Cosmic Radiation and More
Q&A With ESA's Jan Tauber on Cosmic Radiation and More
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Friday, March 20, 2015

Delisting Endangered Species, Ring Around the Solar System, and 50 Years of Spacewalking

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Life on the 'Delist': Are These Animals No Longer Endangered?
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  Join Us for a Live Session With ESA Scientist Jan Tauber
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Watching Memories Slip Away
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Cannibal Shrimp, Ice on Mercury, and Why to Turn Off Food TV
A huge geomagnetic storm struck the Earth, causing auroras to appear far further south than normal. Shrimp infected with the parasite Pleistophora mulleri turn into ravenous cannibals. Breast biopsies are useful for detecting cancer, but not all that great at identifying other kinds of breast abnormalities...[Read More]
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