antoine lavoisier found that mass was conserved in chemical reactions when he saw that

answer; /// the above statement is (true);

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.

it would be kevlar ^^

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.