The velocity required for an object to completely escape Earth's gravitational field is known as the escape velocity. It depends on the mass of the Earth and the distance from the center of the Earth to the object. The average escape velocity from the Earth's surface is approximately 11.2 kilometers per second (km/s) or 40,270 kilometers per hour (km/h), which is equivalent to about 6.95 miles per second (mi/s) or 25,020 miles per hour (mph).
However, it's important to note that reaching escape velocity does not mean that an object will immediately leave Earth's gravitational influence. Gravity extends infinitely into space, gradually decreasing in strength as you move away from the Earth. To completely escape the gravitational pull, an object needs to achieve sufficient velocity to counteract the gravitational force pulling it back.
Additionally, factors such as atmospheric drag, air resistance, and the presence of other celestial bodies can affect the actual velocity required for an object to leave Earth's gravitational field.