The "work required" is ambiguous without saying what force is doing the work on what system. We can safely assume that the system is the satellite, but what about the force that is doing the work on it? You say
malawi_glenn said:
that it is only the vertical work that is asked for
but you also omit specifying the force that does this "vertical work." There are two candidates, gravity and engine thrust.
Is it gravity? I don't think so because we don't use the force of gravity to do the "required" work that results in the necessary kinetic energy to launch satellites. Therefore it must be thrust and that's where we run into problems. The satellite's state of motion when it gets up there is important. As per the work-energy theorem, the work done by the thrust depends on the kinetic energy of the satellite at 1000 km.
Even if one interprets "orbit" as "altitude", the problem does not specify that the satellite reaches 1000 km with zero kinetic energy. That is an additional assumption that needs to be made. I preferred the assumption that the satellite is launched so that it goes into a circular orbit at 1000 km.
I am with you that it may very well be that the author expected the solver to do a line integral of the gravitational force. If so, why didn't the author just say so and why is the vertical launch stipulation necessary? When the satellite reaches 1000 km, the work done by gravity is independent of the launch direction. If the intent of this problem is to get one to do the line integral, that intent is obfuscated by all this ambiguous orbit and satellite stuff. I think that the author did not think this through completely.
To summarize, the formulation of this problem is unclear because
1. It uses the word "orbit" in a way that can be confused with "altitude."
2. It does not specify what force is doing the "required" work.
3. It does not specify directly or indirectly the satellite's state of motion at 1000 km.
I give this problem a D.