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Dave Shrader wrote:
"If that assertion (I am 240 pounds "mass" on earth. That`s a fact. I am 240 pounds "mass" on moon. That`s a weird assertion!) is true, who changed te density of the moon??" Mass is the bulk of matter though not necessarily equal to its weight. A mass weighing 240 pounds on earth weighs less on the moon because there is less mutual attraction between the moon, of much smaller mass than the earth`s mass, and the object which weighs 240 pounds on the earth. Mass is the property which provides a body with inertia. Mass is the mechanical analogy of inductance. Mass is equal to the weight of a body divided by the acceleration due from gravity (32ft./sec./sec.). This is an expression of Newton`s 2nd law of motion: F = MA, thus M = F/A. Newton`s 1st law says that to move a body at rest, enough force must be applied to overcome its inertia. Newton`s 3rd law says that for every action there is an equal and opposite reaction. The gravitational force of the earth is stated as "1". The gravitational force on the moon is about 0.16 that on earth, so an object weighing 240 pounds on earth would weigh only 38.4 pounds on the moon. Best regards, Richard Harrison, KB5WZI |
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#3
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Gene Nygaard wrote:
"You are talking about something different from mass." Yes. An orbiting astronaut may be weightless due to a particular balance of forces, but he has mass and inertia. We have weight and force. Either weight or force may be expressed in pounds or kilograms. The conversion number I remember and use is: 2.2 pounds equal 1 kilogram. The dictionary says the kilogram is a unit of mass, since a mass can conveniently be accurately represented by an object. That particular object is a cylinder of platinum-iridium alloy, called the international prototype kilogram. This object is preserved in a vault at Sevres, France. Work may be meaasured as force times distance or as pounds times feet. Power is work per unit time. Power may be expressed as foot-pounds per minute. James Watt`s horse was said capable of working at a rate of 33,000 foot-pounds per minute. I calculate that as 250 kilogram-feet per second or 76.2 kilogram-meters per second. Best regards, Richard Harrison, KB5WZI |
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