# Theory of Relativity help

• Feb 28th 2010, 10:56 AM
bigdogsmhs306
Theory of Relativity help
I have another problem that i am stuck on

Attachment 15682

m0 is the rest mass and c is the speed of light. What happens as v goes to c-

can anyone help me out i little i have been looking at this on too long and i am getting confused.

Thanks
• Feb 28th 2010, 11:03 AM
e^(i*pi)
Quote:

Originally Posted by bigdogsmhs306
I have another problem that i am stuck on

Attachment 15682

m0 is the rest mass and c is the speed of light. What happens as v goes to c-

can anyone help me out i little i have been looking at this on too long and i am getting confused.

Thanks

As $\displaystyle v \, \rightarrow \, c$ then $\displaystyle 1-\frac{v^2}{c^2} \, \rightarrow \, 1-1 = 0$

As the denominator of a fraction tends to 0 the variable being measured gets infinitely large, in this case m gets infinitely large.

Since division by 0 is undetermined then an object travelling at c would have undetermined (but very large) mass. This means that nothing can travel at c.

To summarise as $\displaystyle v \, \rightarrow \, c \: \: \text{ , } \: m \, \rightarrow \, \infty$
• Feb 28th 2010, 11:10 AM
bigdogsmhs306
ok so if

$\displaystyle v \, \rightarrow \, -c \: \: \text{ , } \: m \, \rightarrow \, -\infty$

would that be right or not
• Feb 28th 2010, 11:13 AM
e^(i*pi)
Quote:

Originally Posted by bigdogsmhs306
ok so if

$\displaystyle v \, \rightarrow \, -c \: \: \text{ , } \: m \, \rightarrow \, -\infty$

would that be right or not

No, it wouldn't be right. Think about what happens when you square a number
• Feb 28th 2010, 11:21 AM
bigdogsmhs306
oh ok ya that is right because anytime that you square a number it is always positive.