Posted by y912f on .
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,
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,
(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 kmtomiles factor 
trigonometry 
y912f,
my choices are
2094.4 mph
209.4 mph
1047.2 mph
104.7 mph 
trigonometry 
Damon,
LOL  the textbook writer is using a calculator with pi on it but not the unit conversions :)

correction 
Damon,
v = 4000 miles (2 pi/ 24 hr)
=1047.2 miles/ hour 
trigonometry 
mysterychicken,
thnks