Originally Posted by
Tclack 1. The problem statement, all variables and given/known data
A satellite is in an orbit around earth. The distance from the center of the earth is described by
r= 4995/(1+.12cos@) R earth= 3960 mi
find the rate at which the altitude is changing at the instant where @=120 degrees. d@/dt= 2.7 degrees/min
2. Notes
altitude equals r - (R earth)
"@" describes the angle the satellite forms with the Perigee of earth (the closest point)
3. The attempt at a solution
a = r - (R earth) = 4995/(1+cos@) - 3960
da/dt= [-4995(-sin@)d@/dt]/(1+cos@)^2
by plugging in the values I get: ~ 46,700 mi/min
The answer from back of book is 27.7 mi/min
I do find it a mystery that the R earth is not used, that may be a key to solving it. Help!