The Physics Factbook
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
|Zeitgeist, Paul W. & Robert F. Neff. Physics: Principles and Problems. New York: Glencoe, 1995: 94.||"A medium-sized apple weighs about one newton."||apple|
|Lafferty, Peter & Julian Rowe. The Dictionary of Science. New York: Helicon, 1993: 404.||"The weight of a medium size (100 g/3 oz) apple is one newton."||apple|
|Setford, Steve. Science Facts. New York: DK Publishing, 1996: 72.||"This apple weighs about 1 N."||apple|
|Hewitt, Paul G. Conceptual Physics. Menlo Park, California: Addison-Wesley, 1987: 33.||"The SI unit of force is the Newton (named after guess who?). One Newton is equal to a little less than a quarter of a pound (like the weight of a quarter-pound burger after it is cooked)."||hamburger|
|Kuhn, Karl F. Basic Physics: A Self - Teaching Guide. 2nd ed. New York: Wiley, 1996: 16.||"A Newton is about ¼ pound, the weight of a stick of margarine."||stick of margarine|
Weight is the downward force of gravity exerted on an object by the planet it is located on. The weight, W, of an object can be determined by the formula …
m is the mass of the object
g is the acceleration due to gravity
G is the universal gravitational constant
M is the mass of the planet
r is the distance
Therefore, the formula for the acceleration of gravity is …
The acceleration due to gravity at the Earth's surface is determined to be approximately 9.81 m/s2. However, when the distance r is greater than the radius of the Earth, g is less than 9.81 m/s2 and thus the weight is less. For example, an object on top of a mountain weighs less compared to it being on the surface. Therefore, the weight of an object is variable with location.
The SI unit of weight is the Newton [N = kg·m/s2], named after Sir Isaac Newton for his work on Newtonian mechanics. One Newton on the surface of the Earth is equal to 101.972 grams, 0.224809 lb, or 3.59694 oz. Objects that weigh one Newton on the Earth's surface include a quarter-pound burger, a stick of margarine, and coincidentally a medium size apple given the alleged story of how Newton discovered gravity.
Wai Wing Leung -- 2004
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