C. Because protons are the identity of the atom.
Magnetism.
HOPE THIS HELPS !
Explanation:
It is given that,
Mass of an electron, 
Initial speed of the electron, 
Final speed of the electron, 
Distance, d = 5 cm = 0.05 m
(a) The acceleration of the electron is calculated using the third equation of motion as :



Force exerted on the electron is given by :



(b) Let W is the weight of the electron. It can be calculated as :



Comparison,


Hence, this is the required solution.
Answer:
If F is a constant, we can take f = 1
f = m×a
ma = 1
therefore we can say that force is hence proportinal to the product of mass and acceleration.