Asingle brick falls with acceleration g. the reason a double brick falls with the same acceleration is

EVERYTHING falls with the same acceleration near the earth's surface.

I thought about this for many years.  I finally understood WHY, and here's the way I like to explain it:

-- It takes MORE FORCE to accelerate a larger mass, and LESS FORCE to accelerate a smaller mass.

-- But guess what !  Gravity exerts MORE FORCE on a larger mass, and LESS FORCE on a smaller mass.

So everything averages out, and the acceleration is always the same, no matter what's falling.

To say it just a little bit differently:

-- A larger mass NEEDS more force to accelerate, but it GETS more force from gravity.

-- A smaller mass NEEDS less force to accelerate, but it GETS less force from gravity.

So everything averages out, and the acceleration is always the same, no matter what's falling.

radiation

explanation:

heat is transmitted by radiation

heats surface water up