Something that there is only so many of or not enough of
Answer:
0.075 T
Explanation:
When a current-carrying wire is immersed in a region with magnetic field, the wire experiences a force, given by

where
I is the current in the wire
L is the length of the wire
B is the strength of the magnetic field
is the angle between the direction of I and B
In this problem we have:
L = 0.65 m is the length of the wire
I = 8.2 A is the current in the wire
F = 0.40 N is the force experienced by the wire
since the current is at right angle with the magnetic field
Solving the formula for B, we find the strength of the magnetic field:

To solve this problem it is necessary to apply the concepts related to the flow as a function of the volume in a certain time, as well as the potential and kinetic energy that act on the pump and the fluid.
The work done would be defined as

Where,
PE = Potential Energy
KE = Kinetic Energy

Where,
m = Mass
g = Gravitational energy
h = Height
v = Velocity
Considering power as the change of energy as a function of time we will then have to


The rate of mass flow is,

Where,
= Density of water
A = Area of the hose 
The given radius is 0.83cm or
m, so the Area would be


We have then that,



Final the power of the pump would be,



Therefore the power of the pump is 57.11W
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.