Text Box: Time

Text Box: http://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm NIST-F1, the nation's primary time and frequency standard, is a cesium fountain atomic clock developed at the NIST laboratories in Boulder, Colorado. NIST-F1 contributes to the international group of atomic clocks that define Coordinated Universal Time (UTC), the official world time. Because NIST-F1 is among the most accurate clocks in the world, it makes UTC more accurate than ever before. The uncertainty of NIST-F1 is continually improving. In 2000 the uncertainty was about 1 x 10-15, but as of January 2013, the uncertainty has been reduced to about 3 x 10-16, which means it would neither gain nor lose a second in more than 100 million years! The graph below shows how NIST-F1 compares toprevious atomic clocks built by NIST. It is now approximately ten times more accurate than NIST-7, a cesium beam atomic clock that served as the United State's primary time and frequency standard from 1993-1999.

http://www.time.gov/

The SI unit of time is the second. The second is the duration of 9,192,631,770 wave periods of emitted radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.

 

The second was defined originally as the fraction 1/86,400 of the mean solar day. The exact definition of "mean solar day" was left to astronomical theories. However, measurement showed that irregularities in the rotation of the Earth could not be taken into account by the theory and have the effect that this definition does not allow the required accuracy to be achieved. In order to define the unit of time more precisely, a definition given by the International Astronomical Union, which was based on the tropical year was adopted in 1960. Experimental work had, however, already shown that an atomic standard of time-interval, based on a transition between two energy levels of an atom or a molecule, could be realized and reproduced much more precisely. Considering that a very precise definition of the unit of time is indispensable for the International System, decided to replace the definition of the second in 1967 using a cesium atom in its ground state at a temperature of 0 K. This was affirmed in 1997.

http://physics.nist.gov/cuu/Units/second.html

Time is a relative quantity, just as weight, it varies with gravity. It also behaves non-intuitively, having ÒquantumÓ effects. However, the second, a unit of time, like mass, is a constant. It is a standard independent of gravity, and like mass is the same on earth, on the moon, and in space.

 

Questions:

1.     It takes Chris 30 minutes to walk to chemistry class on most days. If he drives, it takes him about 1/2 of that time. When Chris walks to class, he normally leaves at 11:45 not to be late. If Chris drives to class, what is the latest time he should leave to get there in time for the opening i-clicker question?

 

2.     Melissa is planning for her first hour exam in which she will have 85 minutes to answer: 20 multiple choice questions (4pts each), 10 True/False questions (2pts each), 1 matching question that includes 10 vocabulary terms (5pts), 1 unit conversion problem (3pts), 1 mathematical density problem (6pts), 1 atomic structure problem (6pts).  Melissa practiced doing the various types of questions and was confident that she could answer any multiple choice question in less than 200 seconds based on the in-class i-clicker questions, conversion problems took her no longer than 4 minutes, matching less than 3 minutes, and most density problems 8 minutes. How much time will she have left for the atomic structure problem?

 

3.     If Melissa, who was an intern in NASAÕs community college summer astronaut program, decided that she would take the first hour exam in the NASA weightless simulator she trained on, thinking that this will provide her with more time for the exam if she does. Briefly explain if this is a theoretically well-founded idea or not.

 

4.     Harry had two final exams on the same day. The first exam lasted from 8:00 a.m. to 10:00 a.m. The second was scheduled to begin at 3:00 p.m. Harry took public transportation to get to and from campus, which took 48 minutes door-to-door. If Harry went home after the first exam to study at home and took the 2:30 BART train to return how much time did he have before the second exam began?

 

5.     Usain Bolt holds the current worldÕs track record for the 100m dash @ 9.58 seconds.
https://www.youtube.com/watch?v=NHmEpqUFLZ8
If Usain could keep this speed over 1 mile what would be his time? (The current worldÕs record for the mile is 3 hours, 43 minutes, 13 seconds.) https://www.youtube.com/watch?v=Ji0yK7fV5Rk
How many miles per hour does the fastest man in the world run?