Answer:
The momentum is 1.94 kg m/s.
Explanation:
To solve this problem we equate the potential energy of the spring with the kinetic energy of the ball.
The potential energy 
of the compressed spring is given by
,
where 
is the length of compression and 
is the spring constant.
And the kinetic energy of the ball is
When the spring is released all of the potential energy of the spring goes into the kinetic energy of the ball; therefore,
solving for 
we get:
And since momentum of the ball is 
,
Putting in numbers we get:
The magnetic force (Lorentz force) experienced by the proton in the magnetic field is given by
since
, because the velocity v and the force F in this problem are perpendicular, and so also the angle
between the velocity and the magnetic field B should be
.
Let's find the magnitude of the magnetic field; this is given by
To understand the direction, let's use the right-hand rule:
-index finger: velocity
- middle finger: magnetic field
- thumb: force
Since the velocity (index) points east and the force (thumb) points south, then the magnetic field (middle finger) points downwards. So we write:
B = -0.091 T
