Alittle boy pushes a wagon with his dog in it. the mass of the dog and the wagon together is 45 kg. the wagon accelerates at .85 m/s2. what force is the boy pulling with?

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.