EvoN1020v Posted May 17, 2006 Share Posted May 17, 2006 What's the difference between the formula of [math]g = \frac{F_g}{m}[/math] and [math]abs(g) = G\frac{m}{r^2}[/math]? Note: abs(g) means absolute value. I don't know the latex code to input absolute. Because the question asked me: Calculate the gravitational field intensity 340 km above the planet Venus. I used the second formula above, where r = 340,000 m; G = 6.67 x 10^-11; m = 4.83 x 10^24 kg. I got [math]2786.859862 \frac{N}{kg}[/math] for the answer. Is this correct? I still don't know why I used the second formula, not the first one, though? Link to comment Share on other sites More sharing options...

Perturbation Posted May 17, 2006 Share Posted May 17, 2006 They're the same thing. [math]\mathbf{g}=\frac{\mathbf{F}}{m}[/math] The force is just [math]G\frac{mM}{r^2}\hat{\mathbf{r}}[/math] To get the absolute value just whack | around the things your taking abs of, there should just be a key on your keyboard for it. Link to comment Share on other sites More sharing options...

EvoN1020v Posted May 18, 2006 Author Share Posted May 18, 2006 All right thanks. Link to comment Share on other sites More sharing options...

Klaynos Posted May 18, 2006 Share Posted May 18, 2006 Because the question asked me: Calculate the gravitational field intensity 340 km above the planet Venus. I used the second formula above' date=' where r = 340,000 m; [/quote'] Just a query, but r is the distance from the centre of the mass NOT the surface... so is that what they mean by "above the planet"??? Link to comment Share on other sites More sharing options...

EvoN1020v Posted May 18, 2006 Author Share Posted May 18, 2006 Just a query, but r is the distance from the centre of the mass NOT the surface... so is that what they mean by "above the planet"??? Yup, I just noticed that in my textbook. I have to find the distance that runs toward the Venus's centre, and add it to the distance "above the surface". Thanks. Link to comment Share on other sites More sharing options...

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