More astrophysics questions!

[Jay-qu]

Good point. If the Earth can be compacted down, then it might become a black hole. Didn't think of that. However, is it actually possible to compact the Earth that much? The energy required for doing that is absolutely immense. The only way I can think of with that happening is if it is swallowed by a black hole, but then it would not become a black hole, it would join one.

not might, will. This is what you are missing, some stars are big enough to collapse in on themselves when their fusion runs out and gravity takes over. Smaller stars and planets cant crush themselves small enough with their own gravity, but remember gravity is the feeblest force, if by some means you could compact it small enough, the earth would become a black hole.

[infamous]

not might, will. This is what you are missing, some stars are big enough to collapse in on themselves when their fusion runs out and gravity takes over. Smaller stars and planets cant crush themselves small enough with their own gravity, but remember gravity is the feeblest force, if by some means you could compact it small enough, the earth would become a black hole.

Very true Jay-qu, there are a few scientists that have even proposed creating mini black-holes in the laboratory setting. Granted, these experiments are far beyond our current technology but not beyond theoretical possibilities............................Infy

[Jay-qu]

For a start the only stupid question is an un-asked one!

 

force between two object due to gravity:

 

[math]F={M_1M_2G}/{R^2}[/math]

 

where M1 and M2 are the masses of the two objects, R is the distance between them and G is the gravitational constant.

 

now basic newtonian mechanics: F=ma

 

hence

 

[math]ma={M_1M_2G}/{R^2}[/math]

 

but if the mass in question is the one been accelerated:

 

[math]a={M_2G}/{R^2}[/math]

 

where M_2 will be the mass of the earth, so here you can see that it doesnt matter what mass the object will be it will always fall at the same rate.

 

If you solve for the mass of the earth and the radius of the earths surface you will get 9.8m/s/s or g.

 

Sorry to bring some maths into it, but its how it works..

 

Also to answer your other question about the moons gravity, if you solve that last equation:

 

[math]a={M_2G}/{R^2}[/math]

 

for the moons mass and radius, you will find that it is 9.8/6m/s/s - one sixth of earths. This is because even though the moon has 1/4 mass its radius is more, ie it is less dense, wich lowers the gravitational field at the surface.

 

J :)

[Jay-qu]

Same in the respective directions, yes. (only saying that to negate the resultant force that is applied in the car situation due to also still experiencing the earths gravitational force)