2001 HSC Q24 part b (1 Viewer)

[_random_]

2001 HSC Q24 part b...HELP

does anyone know how to do this?

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2001exams/pdf_doc/gen_mathemat_01.pdf

I know you have to find the angular distnace to find the time diff, but how do you find angle diff??

 

[lizzieee_]

This one???

In this diagram of the Earth, O represents the centre and G represents Greenwich. The point A lies on the equator.

(i) What is the time difference between Greenwich and point A? (Ignore time zones.) (ii) What is the latitude of pointB?
(iii) Calculate,to the nearest kilometre,the great circle distance from point A to point
B. (You may assume that the radius of the Earth is 6400km, andthat 1 nautical
mile =1.852km.)


ok now.

part (i) since time only changes along the longitudes, (so G & C would be in the same time zone, despite the fact that theyre in different hemispheres, but G & A are different.)

so you basically need to find the time difference between the longitude A is on & the longitude G is on. lol am i losing you?

anyway, so to do that you get the angle between A's longitude & G's longitude, which is already done for you!

yay!

next, one degree = 4mins i think, (check it to make sure!) so 15 degrees = i hour.

divide the angle between the longitudes, 75 by 15, which is 5. and you got the number of hours the are apart! (......5 hours)


whew im tired. ill come back and do the rest in a minute.

 

[lizzieee_]

ok.
part (ii) the latitude is the horizontal line. A is on the equator, so B is 70 degrees above the equator, which is given to you. yay! so that means the latitude of B is 70degreesN (north). thats pretty easy.

part (iii) the great circle is basically the circumference of the sphere. in this case its the equator of the earth.

to find the distance, its like finding the length of the sector of a circle. so you get the angle between the two sides - 75 degrees. yay! now, its like calculating the circumference of a circle, only you use a fraction -

75/360 x 2 x pi (wheres that on the keyboard?) x the radius which theyve given to you as 6400km. yay!

sooooooo....... do that and you get your answer, but i havent got my calculator with me so i don't know what the hell it is..... but your answer will be in nautical miles and youll need to convert it to kilometres, which they tell you how to do,
1 NM = 1.852km. yay!

so basically thats it, hope i wasnt too confusing

 

[_random_]

thank uuuuuu, had trouble getting my head around the first part, but thanks makes alot more sense now...