i think this is the incomplete page that you are showing but the answer is
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Answer:
Let No be initial no of atoms
N = N0 / 2 after 1 half-life
N = N0 / 4 after 2 half-lives
So after 2 half-lives 20 of the 80 atoms remain
Force can be expressed as the product of mass and acceleration. Mathematically, that's F = m(a). Plugging the given into the equation, we have F = (13.5 kg)(9.5 m/s²) = 128.3 kg.m/s² or 128.3 N<span>. </span>
<span>Matter is considered by modern scientists to be anything in the universe that takes up mass. It can be in any state including solid, liquid, or gas. It can also hold potential and or kinetic energy.</span>
