The first thing that needs to be done is to find everything in the same units. 12 hours becomes 43200 seconds. Then find the distance traveled by light in that amount of time. Using the formula v=d/s, manipulate it so it looks like d=v*s. Then plug in the values: d=(3x10^8)*43200, d=1.3x10^13m. But you need to find this in kilometers. To do this, simply divide your answer by one thousand. Thus, a laser beam would travel 1.3x10^10 kilometers in 12 hours.
(a) We can find the current flowing between the walls by using Ohm's law:

where

is the potential difference and

is the resistance. Substituting these values, we get

(b) The total charge flowing between the walls is the product between the current and the time interval:

The problem says

, so the total charge is

The current consists of Na+ ions, each of them having a charge of

. To find the number of ions flowing, we can simply divide the total charge by the charge of a single ion:
Answer:
don't know what class are you you are using which mobile or laptop
Answer:
A.
Explanation:
an atom that has most of its mass is electrons.