CSUN Universal Times and Measures Questions

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Ybirsha95

Science

California state university Northridge

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Objective: This activity introduces the concept of universal time and how it relates to local time. Also introduced are different means of expressing angular and time measurements. By the completion of this unit the student should be able to: 1. Convert time between local and universal times. 2. Convert angular measurements between arc units and decimal form. Background: Time Units: hours [h], minutes [m], seconds [s] Time Unit Conversions: 1h = 60m 1m = 60s Arc Units: degrees [°], arc minutes ['], arc seconds ["] One circle contains 360° Arc Unit Conversions: 1° = 60' 1' = 60" Time measures the passage of events. For us the most dominating recurrent change is the rising and setting of the Sun. It naturally follows that our time scales would be referenced to the position of the Sun. Our current system of time divides the day into 24 hours. There are 360° in a circle and 24 hours in a day, so in one hour the Earth will rotate 15 degrees. It then takes 4 minutes for the Earth to rotate one degree. Universal Time: In astronomy it is convenient to have a time that is the same everywhere on Earth. This is called Universal Time (UT) or Greenwich Mean Time (GMT). It ranges from 0h to 24h. When it is midnight at Greenwich, in England it is 0 UT. Standard Time: For civilization to work, the time has to be the same for a fairly large geographical area centered on the same Longitude. We would not want San Francisco to be say 15min behind us in time. For this reason time zones where invented that span 15 degrees of Longitude. We are located in the Pacific Time Zone, and our time is called Pacific Standard Time (PST). We have an 8 hour time difference from Universal Time. In the Spring, when we switch over to Daylight Savings time it is a 7 hour difference from UT. This time is called Pacific Daylight Time (PDT). International Date Line: The International Date Line was invented because it is impossible for the date to be the same everywhere on earth. Assume it is 12:05 pm somewhere on the planet, then somewhere else it must be 12:05 am. Since the difference in longitude is 180 degrees a new day has to be beginning at the location with the 12:05 am time. The International Date Line was established with a longitude of 180 degrees which turns out for our planet to be perfect since it is in the middle of the Pacific Ocean without any large land masses. If you are traveling west and cross the date line you will need to add a day to you watch. It you are traveling east you will need to subtract a day. Some Examples: Convert from UT to PST: 1.) Convert from 21:35 UT on May 21 to PST 21:35 UT - 8:00 = 13:35 PST on May 21 2.) Convert from 6:35 UT on May 21 to PST 6:35 UT - 8:00 = -2:35 = 22.35 PST on May 20. If the result is negative subtract the hours from 24. Convert from PST to UT: 3.) Convert from 14:35 PST on May 21 to UT 14:35 PST + 8:00 = 22:35 UT on May 21 4.) Convert from 18:35 PST on May 21 to UT 18:35 PST + 8:00 = 2:35 UT on May 22 Time Unit Conversion: Converting from hours, minutes and seconds into just hours expressed in decimal form, and vice versa: 5h38m = (5 + 38/60)h = (5 + 0.633)h = 5.63h 5.63h = 5h and (0.63 x 60)m = 5h37.8m 5h37.8m = 5h and 37 min and (0.8 x 60) = 5 h 37m 48s Arc Unit Conversion: Converting from degrees and arc minutes into just degrees expressed in decimal form, and vice versa: 24°26' = (24 + 26/60)° = (24 + 0.43)° = 24.43° 24.43° = 24° and (0.43 x 60)' = 24°25.99' = 24°26'
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Cambridge International Examinations
Cambridge International Advanced Subsidiary and Advanced Level

MATHEMATICS

9709/42
May/June 2016

Paper 4
MARK SCHEME
Maximum Mark: 50

Published

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.
Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.
Cambridge will not enter into discussions about these mark schemes.
Cambridge is publishing the mark schemes for the May/June 2016 series for most Cambridge IGCSE®,
Cambridge International A and AS Level components and some Cambridge O Level components.

® IGCSE is the registered trademark of Cambridge International Examinations.

This document consists of 8 printed pages.
© UCLES 2016

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Mark Scheme
Cambridge International AS/A Level – May/June 2016

Syllabus
9709

Paper
42

Mark Scheme Notes
Marks are of the following three types:
M

Method mark, awarded for a valid method applied to the problem. Method marks are
not lost for numerical errors, algebraic slips or errors in units. However, it is not
usually sufficient for a candidate just to indicate an intention of using some method or
just to quote a formula; the formula or idea must be applied to the specific problem in
hand, e.g. by substituting the relevant quantities into the formula. Correct application
of a formula without the formula being quoted obviously earns the M mark and in some
cases an M mark can be implied from a correct answer.

A

Accuracy mark, awarded for a correct answer or intermediate step correctly obtained.
Accuracy marks cannot be given unless the associated method mark is earned (or
implied).

B

Mark for a correct result or statement independent of method marks.



When a part of a question has two or more “method” steps, the M marks are generally
independent unless the scheme specifically says otherwise; and similarly when there are
several B marks allocated. The notation DM or DB (or dep*) is used to indicate...


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