Relativistic mass and the speed of light limit

[feynmann]

Is the relativistic mass the reason that objects with mass cannot reach the speed of light?

>> The book gave it as the explanation of why objects with mass cannot reach the speed of light. The book says that as the object increases its speed its mass increases making it require more energy to speed up, ultimately ending in it requiring an infinite amount of energy to raise its speed.

 

[JesseM]

You're free to think of it this way, but it's easier to just think in terms of the object's energy--for an object with nonzero rest mass the energy would approach infinity in the limit as its speed approached c, so no finite amount of energy you apply to a mass to push it will ever get it to c.