Answer:
,Assume that the average volume of an adult human body is one-tenth
cubic meter (0.10 m) and that there are two billion (2.0 x 109)
adults in the world.
a. What would be the total volume of all the adults in the world?
b. Compute the length of one edge of a cubic container that has a
volume equal to the volume of all the adults in the world.
I’ve done this before the answer is B
A) d. 10T
When a charged particle moves at right angle to a uniform magnetic field, it experiences a force whose magnitude os given by

where q is the charge of the particle, v is the velocity, B is the strength of the magnetic field.
This force acts as a centripetal force, keeping the particle in a circular motion - so we can write

which can be rewritten as

The velocity can be rewritten as the ratio between the lenght of the circumference and the period of revolution (T):

So, we get:

We see that this the period of revolution is directly proportional to the mass of the particle: therefore, if the second particle is 10 times as massive, then its period will be 10 times longer.
B) 
The frequency of revolution of a particle in uniform circular motion is

where
f is the frequency
T is the period
We see that the frequency is inversely proportional to the period. Therefore, if the period of the more massive particle is 10 times that of the smaller particle:
T' = 10 T
Then its frequency of revolution will be:

Snapping a leaf shut around an insect, I think.