The Physics
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Weight of an Apple

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Zitzewitz, Paul W. Robert F. Neff. Physics: Principles and Problems. New York: Glencoe, 1995: 94. "A medium sized apple is about 1 N" 1 N
Kitchen Reference Guide. Apple Journal. 28 May 2009. "1 pound equals approximately 3 medium apples or 2 cups sliced." 1.48 N
P H, Borcherds. Measure for Measure: The Story of Imperial, Metric and Other Units. European Journal of Physics 25 (2004): 695-696. 28 May 2009 "Last year in our garden we picked an apple which weighed one pound, thirteen and a half ounces (1 lb 13½ oz or 29½ oz). The following day we went to an Apple Day event where there were many exotic apples on display, varieties which are not sold in shops. One of the varieties there was called 'Twenty Ounce'…. The SI unit of force is the Newton, which is very appropriate since the Newton is about the weight of an average apple. Not of course the weight of a Twenty Ounce apple, whose weight is about 5 N." 1 - 8 N
D. Neilsen, B. Fallahi, G. Neilsen, F. Peryea. Development and Evaluation of a Bitter Pit Prognosis Model in Apple Orchards in the South Tyrol (Northern Italy). Acta Horticulturae. (ISHS) 564: 91-96. "For 13 years fruit samples were taken in experimental orchards for analyses at the beginning of July, when the fruitlets have an average weight of 70 g." 0.7 N
Teacher Guide: Karate. Newton's Apple. Twin Cities Public Television. 2006. "Newton: unit of measure of force. Approximately equal to the force exerted by the weight of an apple." 1 N

Weight is a term that is usually used loosely in lay people's conversation. The way that the word is most commonly used today is more descriptive of the object's mass than its actual weight. Weight is actually defined as the magnitude of the gravitational force acting on an object on or near the Earth's surface. This concept is illustrated in the equation

w = mg = GmEm2/r2

where mE is the mass of Earth, and r is the distance between the object and the center of the Earth. r would be equal to the radius in the instance that the object is resting on Earth's surface. G is the universal gravitational constant and is equal to 6.67*10−11 Nm2/kg2 and g is the acceleration due to gravity. The SI unit for mass is the kilogram [kg].

Weight is measured in newtons, N, or kgm/s2. One Newton is defined as a force that causes a 1 kg object to accelerate 1 m/s2. One Newton is 0.225 pound. An apple is an ideal example for such comparison. Apples weight is dependent upon species, the amount of nutrients it receives and its size. The average apple is between 70 and 100 grams or 0.33 pound or 0.7 and 1N. This idea is ironic as it is often believed that it was a fallen apple that inspired Sir Isaac Newton's ideas about gravity.

Alicia McGeachy -- 2009

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