# How does E=mc² work?

I know the basics of E=mc² and it being mass energy, but someone told me its also used for projectiles and explosions how does it corrolate with destructive power ?

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HallsofIvy
Homework Helper
If you know what "$E= mc^2$" means then you should be able to work that out. It does not really have anything to do with "projectiles" since that does not change mass into energy. In a nuclear explosion some mass (typically a tiny fraction of the total mass) is converted to energy. Now what that is in "destructive energy" depends on exactly what you mean by "destructive energy". Not all of that energy "destroys" things.

Ah that claifys things, and sorry I didn't specify what I ment in destruction, our convo was talking about a astroid striking earth, he said E=mc² is what is used used to measure it , it sounded suspicious so I came here to ask some more experienced people

Isaac0427
Gold Member
Ah that claifys things, and sorry I didn't specify what I ment in destruction, our convo was talking about a astroid striking earth, he said E=mc² is what is used used to measure it , it sounded suspicious so I came here to ask some more experienced people
I'm not sure how that works. Sorry.

nicholas0211510
I'm not sure how that works. Sorry.
alright, I guess I'll just do some reading on line

Appreciate the help

jbriggs444
Homework Helper
2019 Award
Ah that claifys things, and sorry I didn't specify what I ment in destruction, our convo was talking about a astroid striking earth, he said E=mc² is what is used used to measure it , it sounded suspicious so I came here to ask some more experienced people
E=mc2 is not what is used to measure the destructive power of an asteroid striking earth. The fellow who said it was... was mistaken.

If one wanted to determine the energy released in an impact with such an asteroid, E=1/2mv2 would be the appropriate measure.

Nugatory, Isaac0427, Mentallic and 1 other person
CWatters
Homework Helper
Gold Member
The problem is the difficulty of converting mass to energy. Simply colliding an asteroid into a planet isn't going to do it. As others have said, that's not the right kind of interaction.

In an atomic explosion some of the mass is converted to energy. Google found references that suggest for the Little Boy bomb only about 600mg of 64kg was turned into energy. That's a very low percentage of the total mass but a heck of a lot of energy.