Posted by **y912f** on Wednesday, January 7, 2009 at 8:02pm.

assuming that Earth's radius is 6400 km, find the linear velocity of Quito, Equador, a city on the equator. (Use pi=3.1416 and 1.6 km=1 mile).

- trigonometry -
**Damon**, Wednesday, January 7, 2009 at 8:08pm
I guess we are to do miles per hour ?

v = omega * r

omega = 2 pi /24 hr

r = 6.4*10^3 km (1 mile/1.6 km) = 4,000 miles

so

v = 4000 miles (2 pi/ 24 hr)

=3333 miles/ hour

- trigonometry -
**drwls**, Wednesday, January 7, 2009 at 8:09pm
(2 pi * 6400 km)/(24 hours)

That will give you the answer in km/h. Divide by 1.6 for miles per hour.

Actually, a better conversion factor with five significant figures is 1.6093 km/mile

It makes no sense to have five significant figures for pi and only two for the km-to-miles factor

- trigonometry -
**y912f**, Wednesday, January 7, 2009 at 8:13pm
my choices are

2094.4 mph

209.4 mph

1047.2 mph

104.7 mph

- trigonometry -
**Damon**, Wednesday, January 7, 2009 at 8:14pm
LOL - the textbook writer is using a calculator with pi on it but not the unit conversions :)

- correction -
**Damon**, Wednesday, January 7, 2009 at 8:18pm
v = 4000 miles (2 pi/ 24 hr)

=1047.2 miles/ hour

- trigonometry -
**mysterychicken**, Thursday, January 8, 2009 at 11:23am
thnks

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