[desigonzalez]

What is the radius of a black hole made by crushing an apple hard enough? THe apple weights about 1 N on earth.

[urmod4u]

1N weight on earth is 98 gram, right? The mass of the apple is 0.0982 Kg. (Oh, BTW, that is a very small apple, usually there only are 4 to 5 apples in a kg - an apple's weight is around 2 Newton).
Use Newton's laws to calculate the distance to the center where the speed of something falling to it will reach the speed of light. High order mathematics are required. Come back if you don't understand.
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That is what makes me mad. No theoretician has any idea of what is happening around him. They even have no idea of the weight of an apple.
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And this poor boy who asks this question, is only searching for the answer for his homework. He doesn't even want to understand the solution. But of course, this solution, if given to him, will not get him graduated.

[urmod4u]

I'll add some theory to this.
Every mass, when concentrated in a singularity, has a horizon below which light cannot escape.
The larger the mass, the farther away this horizon (or radius) will be.

[urmod4u]

Another hint: speed is sqrt^2gh.
g is function of the distance (h). See Newton's laws. H is infinite.

[desigonzalez]

I think I get it now, thanks a lot. Your explanation was very helpful.