It is salt water because they are two things combined together.
Answer: 
Explanation:
We know the total diameter of the cell (assumed spherical) is:

Then its total radius 
On the other hand, we know the thickness of the cell wall is
and its density is the same as water (
).
Since density is the relation between the mass
and the volume
:

The mass is:
(1)
Now if we are talking about this cell as a thin spherical shell, its volume will be:
(2)
Where 
Then:
(3)
(4)
Substituting (4) in (1):
(5)
(6)
Knowing
and
:
Answer:
The electric field due to the right ring at a location midway between the two rings is 
Explanation:
Given that,
Radius of first ring = 5 cm
Radius of second ring = 20 cm
Charge on the left of the ring = +30 nC
Charge on the right of the ring = -30 nC
We need to calculate the electric field due to the right ring at a location midway between the two rings
Using formula of electric field
Put the value into the formula


Hence, The electric field due to the right ring at a location midway between the two rings is 
as we know that velocity= displacement/change in time
hence velocity here is= 11-3/12-0
=8/12
=2/3
=0.667m/s
hopefully i am right