Gravitational force question...

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MCAT guy

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I was given this as a solution to my problem, my question is, do you know where the 1000 m/km would have come from?

The problem gave the value of earth's mass, the 500 kg satellite, the gravitational constant and the fact that we are exactly 7 radius lengths from the core (7x6400), for the life of me I can't figure out where the 1000 m/km comes from, it was not given. Is this a constant I'm missing (only R is on bottom?)

We could have arrived at the same result had we used Newton's law of universal gravitation. In that case, we would have needed to recall the equation and plug in the values provided in the question. The calculation is shown below:
exam_3_physci_sol_iq33_eq2.gif

Remember, the SI unit of force is called a newton (N), and 1 N = 1 kg•m/s2. Note that it is much quicker to use the simpler, intuitive approach than to risk trying to solve a time-consuming equation.

 
dude. you need to go to sleep 😉

6400 is km according to your solution. Newtons require meters. 1000 meters per kilometer. It's a unit conversion.
 
I think the brain just shuts down occasionally, almost to say "screw you MCAT guy, I'm done for tonight."
 
🙂 haha ohhh don't i understand. my brain has gone on vacation so many times during this studying... it doesn't understand why i'm bringing all this years old junk back up! the mcatfears keep us up long after the brain has quit processing at 100% O.O
 

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