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# Physical Significance of Multiplication

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Hi,

The multiplication sign in p = m x v means that mass 'm' moves with velocity v.

But...

The multiplication sign in E = m x c2 does not mean that mass 'm' moves with speed C.

I find it surprising. Can anyone help me quench my surprise and if possible give some more examples where 'multiplication' has such different meanings, with the terms in the equation being mass and speed/velocity.

Edited by Curious555
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• 4 months later...
Posted (edited)

Dear curious,

Look for this structure

Some constant = x/y

The physical meaning of it would be that x and y are proportional. X and y must grow proportional, othetwise their division would not be a constant.

Let us now rewrite p = mv to m = p/v. This means that p and v are proportional in case m is a constant.

Now look at E = m x c2 . We can rewrite to m = E / c2.

This simply means that E is proportional to the square of c for any specific mass.

Or even better, if we take

c2 = E/m then it says that energy and mass are proportional in case c is a constant.

I hope this helps?

Regards,

Peter Schuttevaar

Edited by PeterSchuttevaar
clearer and more complete explanation

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