# Why is it called “escape velocity” and not “escape acceleration”?

As we know, velocity to escape from an orbit is in proportional with the orbital velocity:

$$v_\mathrm{escape}=\sqrt{2}v_\mathrm{orbit}$$

Since, orbital velocity decreases as we move away so should be velocity to escape from it. In other words farther is an orbit lesser will be velocity to escape from it.

Thus, as we move away the value of velocity with which we need to escape decreases. Now isn't that actually negative acceleration? We need to have that acceleration in order to escape.

Why then we call it as escape velocity instead of escape acceleration?

(And, if I am correct is it just opposite of gravitational acceleration?)

• It doesn't matter how the velocity is achieved; if you have it, you escape; if not, you are stuck. Thus the acceleration is not the deciding factor. – Peter Diehr Feb 16 '16 at 13:30
• Gravity is a constant (negative) acceleration. Technically anything with a positive acceleration is an escape acceleration given enough time. It doesn't make much sense to reason in those terms though, otherwise one could argue that to fly, you need only build a device that grants you constant positive acceleration. – Neil Feb 16 '16 at 14:20
• Are the dimensions of the quantity in question those of velocity or those of acceleration? – dmckee Feb 16 '16 at 17:40