# Relativity mix-up............

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Do Joules divided by Kilograms per Square Meter equal Miles per Hour?

ie does E=mc^2?

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Not quite. The correct expression would be: Joules divided by Kilograms are equivalent to metres-squared per second-squared.

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Not quite. The correct expression would be: Joules divided by Kilograms are equivalent to metres-squared per second-squared.

Newton meters/wg=square of light speed?

I feel that the units are inconsistent.could you break it down for me,please?

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1 joule is, among other things,

• The work done on some object by a force of one newton as the object moves a distance of one meter, from $W=\oint \mathbf F \cdot d\mathbf l$
• The kinetic energy of a 2 kilogram mass moving at the non-relativistic velocity of 1 meter per second, from $KE=\frac 1 2 m v^2$

These expressions have the same fundamental units and the same numerical value:

$1\,\text{joule} = 1\,\text{newton}\,*\,1\,\text{meter} = 1\,\text{kg}\,\text{meter}/\text{second}^2\,*\,1\,\text{meter} = \frac 1 2\,*\,2\,\text{kg}\,*\,(1\,\text{meter}/\text{second})^2$

Energy has units of mass*velocity squared. The expression $mc^2$ has units mass*velocity squared -- energy.

muchos gratias

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