Why do you suppose the stomach contains acid? what do you think happens when there is more acid than food in the stomach? PLZ help I need an answer ASAP
50 points to the first person

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in

Which statement is the best definition of an atom? a) anything that has mass and occupies space. b) the smallest particle that has the properties of an element. c) a substance that cannot be broken down chemically into simpler substances. eliminate d) the smallest unit of a substance that exhibits all of the properties characteristic of that substance.