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1
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the time taken for the radioactivity of a specified isotope to fall to half its original value
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2
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a positively charged ion
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3
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the quantity of motion of a moving body, measured as a product of its mass and velocity.
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4
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a group of similar things or people positioned or occurring closely together
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5
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the moving of something from its place or position
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7
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the temperature at which a liquid boils and turns to vapor
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9
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energy that a body possesses by virtue of being in motion
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10
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is a chemical bond that involves the sharing of electron pairs between atoms
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12
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physical restraints used to hold someone or something prisoner, especially ropes or chains.
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13
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the number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table
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14
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a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force
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15
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an atom or molecule with a net electric charge due to the loss or gain of one or more electrons
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16
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the displacement of the spectrum to shorter wavelengths in the light coming from distant celestial objects moving toward the observer
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19
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the process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge
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21
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the process or result of joining two or more things together to form a single entity
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23
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consisting of two or more simple machines operating together
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24
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each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons
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25
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an obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination.
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26
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the degree of compactness of a substance
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28
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the temperature at which a given solid will melt.
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29
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are formed from the attraction between mobile electrons and fixed, positively charged metallic atoms.
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32
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a celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun
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34
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the distance traveled by an object divided by the time interval during the motion occurred
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38
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a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
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41
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the resistance that one surface or object encounters when moving over another
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42
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the point on the earth's surface vertically above the focus of an earthquake
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43
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the measurable amount of a property, such as force, brightness, or a magnetic field.
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44
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penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei
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45
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the electrostatic force of attraction between two oppositely charged ions
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