Question

Each of the nuclei below is accelerated from rest through the same p.d, which one completes the acceleration with lowest speed?
a)1H1
b)2He4
c)3Li7
d)4Be9
answer is C, but I don't know why...

Answer 1

A force is needed to cause an acceleration.

Electric force F = Eq = (V/d) q = Vq / d

This should be equal to F = ma (the resultant force on the nuclei.).

So, ma = Vq/d giving a = Vq / md

Since V and d are constant for all particles, the acceleration a depends on q/m.

Hence, the acceleration would depend on the charge and mass of the particle. So, the q/m ratio is important. This ratio is also called the specific charge.

The particle that completes the acceleration with lowest speed is that one having the lowest value of this ratio.

The mass is the nucleon number while the charge is taken to be equal to the proton number (since we are dealing with nuclei, and not the atoms).

For 11H, ratio = 1/1 = 1

For 42He, ratio = 2/4 = 0.5

For 73Li, ratio = 3/7 ≈ 0.429

For 94Be, ratio = 4/9 ≈ 0.44

If you are satisfied with this explanation then please mark it as a brainliest answer!