After two half lives how much of the original material has decayed

Explanation: After 1 half life , clearly HALF of the original isotope remains. And after TWO half-lives, a HALF + HALF of a HALF , i.e. 34 of the original mass has decayed.

I think that you need to divide the quantity of the substance in half twice.

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy