Final answer:
A body projected with a speed greater than Earth's escape speed will retain its initial velocity as it enters interstellar space, assuming no other significant forces act upon it.
Step-by-step explanation:
If a body is projected from the surface of Earth with a speed v greater than the escape speed ve, once it reaches interstellar space, away from significant gravitational influences, its speed can theoretically approach v minus ve. However, the practical speed in interstellar space depends on additional factors such as gravitational assists or resistance from interplanetary medium, which are typically negligible at such distances from a star. When an object is projected with the escape speed ve, the speed required to leave Earth and not return, it would theoretically have a residual speed of 0 m/s as it reaches an infinite distance from Earth.
Escape velocity on Earth is approximately 11.2 km/s. When a body is launched at a speed greater than this from Earth, its kinetic energy is sufficient to overcome Earth's gravitational pull completely. Assuming no further forces act on the object once it has escaped Earth's gravity, the body's speed in interstellar space would remain constant at its initial velocity v since there are no significant opposing forces to decelerate it.