Momentum = mass x velocity so if velocity is kept same and mass is increased then momentum will increase.
A charged particle moving in a magnetic field experiences a force equal to:

Thus, the magnitude of the force that the proton experiences is given by:

The magnetic field is perpendicular to the proton's velocity, therefore, we have
. Replacing the given values, we obtain:

32? I could be wrong but I’m going with that answer choice
The final temperature is 83 K.
<u>Explanation</u>:
For an adiabatic process,


Given:-



(the gas is monoatomic)

T = 275
0.30
T = 83 K.