Ceramic is the most brittle of the materials you have specified.
Answer:
4347.8 m/s
Explanation:
It is given that the radius of the circular path traversed by proton and electron is same. Also, we know that magnitude of charge on an electron and proton is same. Magnetic field strength is same for both.

Take the ratio:

He has a mass of 56 kg.
The equation given is PE = mgh.
PE = 4620 J
h = 8.4
g = 9.8
Therefore:
4620 = 82.32m
m = 4620/82.32
m = 56 (rounded to two significant digits)