We learned that our weight is a force (a push or pull)that is determined by both our mass and the acceleration due to gravity that keeps us on the ground. Weight is considered a variable or derived quantity. Mass is the amount of matter in an object and is expressed in units of grams or kilograms. Mass is constant and does not change with location. All objects with mass exert a force of attraction on other objects. This force of attraction is called gravity. Gravity is a function of the mass of the objects and the distance between the objects. The earth has a mass that is six times greater than the mass of the moon. All objects accelerate towards earth at a rate of 9.8 meters per second each second. Acceleration on the moon is only 1.62 meters per second each second. Weight is the force exerted by one mass on to another. For example, each step you take on earth can be measured as a force equal to your weight. The scientific unit for weight is the Newton (N)after our old friend Isaac Newton. You can determine your weight by multiplying your mass in kilograms by the acceleration due to gravity. This formula is also know as Newton's Second Law of Motion. To calculate our weight we must multiply our mass in kilograms times the force of gravity. Here on Earth everything accelerates towards Earth at a rate of 9.8 m/sec/sec.