Answer: D (an object's mass is independent of gravity)

**mass** () A measure of the amount of matter contained in a physical body. Mass is independent of gravity and is therefore different from weight. *See Note at* **weight.**

**weight** () **1.** The force with which an object near the Earth or another celestial body is attracted toward the center of the body by gravity. An object's weight depends on its mass (the amount of matter it consists of) and the strength of the gravitational pull. On Earth, for example, an object weighs less at the top of a very high mountain than it does at sea level, simply because the gravitational pull at the top of the mountain is lower than it is at sea level. **2.** A unit used as a measure of graitational force: *a table of weights and measures.* **3.** A system of such measures: *avoirdupois weight; troy weight.*

**Weight/Mass**

It's easy to convert pounds into kilograms: just multiply the number of pounds by .45 (or if you want greater precision, use .4536). But no matter how many times you do this conversion, you will always be making a mistake, because a pound is a unit of*force,* while a kilogram is a unit of *mass.* A pound is a measure of the force that a gravitational field exerts on an object. As such, a pound is a unit of *weight,* not of mass. An object's mass is its ability to resist changes in the speed or direction of its motion, and it is always the same regardless of what forces are acting upon it. If you were walking on the moon, for example, your mass would be the same as it is on the Earth, but your weight would be one sixth of what it is on the Earth because of the lower gravitational pull of the moon. If this is so, you might ask, how can my science teacher ask me to convert pounds into kilograms? When we make such conversions, we are assuming that the object in question is on the Earth, at sea level, where the conversion factor works for all practical purposes.

It's easy to convert pounds into kilograms: just multiply the number of pounds by .45 (or if you want greater precision, use .4536). But no matter how many times you do this conversion, you will always be making a mistake, because a pound is a unit of