A heavy leather ball and a light tennis ball of equal size are kept on the floor of a moving train. When the train is suddenly stopped they are set in motion. In which direction will they move? Which one of them will attain higher velocity? (assume that friction is same for both).
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Answer:
The Law of Conservation of Mass
The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. If we account for all reactants and products in a chemical reaction, the total mass will be the same at any point in time in any closed system. Lavoisier's finding laid the foundation for modern chemistry and revolutionized science.
The Law of Conservation of Mass holds true because naturally occurring elements are very stable at the conditions found on the surface of the Earth. Most elements come from fusion reactions found only in stars or supernovae. Therefore, in the everyday world of Earth, from the peak of the highest mountain to the depths of the deepest ocean, atoms are not converted to other elements during chemical reactions. Because of this, individual atoms that make up living and nonliving matter are very old and each atom has a history. An individual atom of a biologically important element, such as carbon, may have spent 65 million years buried as coal before being burned in a power plant, followed by two decades in Earth's atmosphere before being dissolved in the ocean, and then taken up by an algal cell that was consumed by a copepod before being respired and again entering Earth's atmosphere (Figure 1). The atom itself is neither created nor destroyed but cycles among chemical compounds. Ecologists can apply the law of conservation of mass to the analysis of elemental cycles by conducting a mass balance. These analyses are as important to the progress of ecology as Lavoisier's findings were to chemistry.