According to the theory of special relativity proposed by Albert Einstein, an object with mass cannot reach or exceed the speed of light in a vacuum, which is approximately 299,792,458 meters per second (or about 670,616,629 miles per hour). As an object with mass approaches the speed of light, its energy requirements increase, and it becomes more difficult to accelerate further.
When an object with mass is already in motion and you add more energy to it, its speed will not increase to exceed the speed of light. Instead, according to Einstein's theory, the object's relativistic mass would increase, and it would require more and more energy to accelerate further. As the object's speed gets closer to the speed of light, the incremental increase in velocity becomes smaller and smaller.
As an object with mass approaches the speed of light, its energy and momentum increase without bound, while its velocity approaches but never quite reaches the speed of light. This phenomenon is described by the relativistic equation for momentum:
p = (m * v) / (sqrt(1 - (v^2 / c^2)))
Where: p is the momentum of the object, m is the rest mass of the object, v is the velocity of the object, and c is the speed of light.
As v approaches c, the denominator of the equation approaches zero, making the momentum (p) effectively infinite. However, the velocity (v) remains less than c.
Therefore, no matter how much additional energy is added to an object with mass already moving at or near the speed of light, it will not go faster than the speed of light. The laws of physics, as described by the theory of special relativity, impose a fundamental limit on the velocity of massive objects.