From: sylvia@not.at.this.address
Erik Max Francis wrote:
> Sylvia Else wrote:
>> Dr J R Stockton wrote:
>>> In sci.space.tech message <97af933c-beda-4dba-aa2e-81364d4202ef@e20g2000
>>> vbc.googlegroups.com>, Tue, 9 Jun 2009 06:09:45, dotcom
>>> posted:
>>>
>>>> I quoted the problem verbatim from my daughters text book.
>>>
>>> In that case, assuming that you actually understand and mean "verbatim",
>>> move the daughter to a different school - one that uses a better grade
>>> of textbook. What you gave cannot be verbatim from a well-written book.
>>>
>>
>> It's not so bad. Although its stated initial speed corresponds to a
>> circular orbit at 2000km (apparently, I haven't checked), the question
>> doesn't say that the satellite is in such an orbit. It does say that
>> it falls to a height of 800km.
>>
>> So the reasonable assumption is that it's in an orbit that allows it
>> to be at 2000km at one point in time, and 800km at another.
>
> That would be my guess, too; it sounds asking what the speed of the
> satellite will be if it has a perigee of 800 km altitude and an apogee
> of 2000 km altitude. It's a bit glib and not terribly clear, though. I
> agree with the others that it's not a very useful question, especially
> for high school students.
>
It couldn't have an apogee at 2000km, because it's going at the wrong
speed. But the question doesn't require any assumptions about the actual
orbit.
I don't really see the objection to the question.
It requires the ability to calculate the potential energy of an object
in a gravitational field, an understanding of kinetic energy, and the
application of the law of conservation of energy.
Is this not highschool maths/physics?
Sylvia.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
