Question

While in empty space, an astronaut throws a ball at a velocity of 11 m/s. what will the velocity of the ball be after it has traveled 4 meters?

Answer 1

In empty space probably means, there is no force on the ball.

(This assumption is not quite correct since there is still the force of gravity between the ball and the astronaut, but this force is very very small and can be neglected.)

Assuming there is no force on the ball, Newtown's 1st law says: When viewed in an internal frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
 
This means:
If there is no force on the ball, there will be no acceleration on the ball either.
If the acceleration is zero, the velocity of the ball never changes.