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| 1248703736 | The condition in which an object is falling without resistance; objects are weightless when in free-fall. | Free-fall | 0 | |
| 1248703737 | Principle that, for any force, there is always an equal and opposite reaction force. | Newton's Third Law of Motion | 1 | |
| 1248703738 | The international unit of energy, equivalent to about 1/4000 of a Calorie. | Joule | 2 | |
| 1248703739 | An encounter in which two (or more) objects pass near enough so that each can feel the effects of the other's gravity and they can therefore exchange energy. | Gravitational Encounter | 3 | |
| 1248703740 | The most commonly used temperature scale in science, defined such that absolute zero is OK and water freezes at 273.15K. | Kelvin (Temperature Scale) | 4 | |
| 1248703741 | The temperature scale commonly used in daily activity internationally, defined so that, on Earth's surface, water freezes at 0°C and boils at 100°C. | Celsius (Temperature scale) | 5 | |
| 1248703742 | The law expressing the force of gravity (Fg) between two objects, given by the formula | Universal Law of Gravitation | 6 | |
| 1248703743 | Momentum attributable to rotation or revolution. The angular momentum of an object moving in a circle of radius r is the product m x v x r. | Angular Momentum | 7 | |
| 1248703747 | The speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star. | Escape Velocity | 8 | |
| 1248703749 | A law followed by any quantity that decreases with the square of the distance between two objects. | Inverse Square Law | 9 | |
| 1248703751 | Orbits on which an object travels repeatedly around another object; bound orbits are elliptical in shape. | Bound Orbits | 10 | |
| 1248703754 | The portion of any object's total velocity that is directed across (perpendicular to) our line of sight. This part of the velocity cannot be measured with the Doppler effect. It can be measured only by observing the object's gradual motion across our sky. | Tangential Velocity | 11 | |
| 1248703757 | Potential energy that can be released through chemical reactions; for example, food contains chemical potential energy that your body can convert to other forms of energy. | Chemical Potential Energy | 12 | |
| 1248703759 | The higher-than-average tides on Earth that occur at new and full moon, when the tidal forces from the Sun and Moon both act along the same line. | Spring Tides | 13 | |
| 1248703761 | The amount of mass per unit volume of an object. The average density of any object can be found by dividing its mass by its volume. Standard metric units are kilograms per cubic meter, but in astronomy density is more commonly stated in units of grams per cubic centimeter. | Density (Mass) | 14 | |
| 1248703763 | The sum of an orbiting object's kinetic and gravitational potential energies. | Orbital Energy | 15 | |
| 1248703766 | A measure of the average kinetic energy of particles in a substance. | Temperature | 16 | |
| 1248703768 | Three basic laws that describe how objects respond to forces. | Newton's Laws of Motion | 17 | |
| 1248703770 | The standard unit of force in the metric system: | Newton | 18 | |
| 1248703772 | Law stating how a net force affects an object's motion. Specifically, force = rate of change in momentum, or force = mass × acceleration. | Newton's second law of motion | 19 | |
| 1248703774 | Principle that, in the absence of a net force, an object moves with constant velocity. | Newton's first law of motion | 20 | |
| 1248703777 | The lower-than-average tides on Earth that occur at first- and third-quarter moon, when the tidal forces from the Sun and Moon oppose each other. | Neap Tides | 21 | |
| 1248703779 | Energy carried by light; the energy of a photon is Planck's constant times its frequency, or h × f. | Radiative Energy | 22 | |
| 1248703782 | A generalization of Kepler's third law used to calculate the masses of orbiting objects from measurements of orbital period and distance; usually written as | Newton's version of Kepler's third law | 23 | |
| 1248703784 | The precise mathematical shape of one type of unbound orbit (the other is a parabola) allowed under the force of gravity; at great distances from the attracting object, a hyperbolic path looks like a straight line. | Hyperbola | 24 | |
| 1248703786 | The coldest possible temperature, which is 0 K. | Absolute Zero | 25 | |
| 1248703789 | The proposed force that exists at very high energies when the strong force, the weak force, and the electromagnetic force (but not gravity) all act as one. | GUT Force | 26 | |
| 1248703792 | Friction within an object that is caused by a tidal force. | Tidal Friction | 27 | |
| 1248703793 | A force that occurs when the gravity pulling on one side of an object is larger than that on the other side, causing the object to stretch. | Tidal Force | 28 | |
| 1248703795 | The rate at which an object's velocity changes. Its standard units are m/s^2. | Acceleration | 29 | |
| 1248703797 | Energy stored for later conversion into kinetic energy; includes gravitational potential energy, electrical potential energy, and chemical potential energy. | Potential Energy | 30 | |
| 1248703799 | The experimentally measured constant G that appears in the law of universal gravitation: | Gravitational Constant | 31 | |
| 1248703801 | The temperature scale commonly used in daily activity in the United States; defined so that, on Earth's surface, water freezes at 32°F and boils at 212°F. | Fahrenheit (Temperature Scale) | 32 | |
| 1248703804 | The collective kinetic energy, as measured by temperature, of the many individual particles moving within a substance. | Thermal Energy | 33 | |
| 1248703806 | A weight of zero, as occurs during free-fall. | Weightlessness | 34 | |
| 1248703809 | A satellite that orbits Earth in the same time it takes Earth to rotate (one sidereal day). | Geosynchronous Satellite | 35 | |
| 1248703811 | Energy of motion, given by the formula 1/2 mv2. | Kinetic Energy | 36 | |
| 1248703813 | The principle that the square of a planet's orbital period is proportional to the cube of its average distance from the Sun (semimajor axis), which tells us that more distant planets move more slowly in their orbits; in its original form, written p2 = a3. | Kepler's Third Law | 37 | |
| 1248703815 | A measure of the amount of matter in an object. | Mass | 38 | |
| 1248703817 | The principle that, in the absence of net torque (twisting force), the total angular momentum of a system remains constant. | Conservation of Angular Momentum (Law Of) | 39 | |
| 1248703819 | The net force that an object ap0plies to its surroundings; in the case of a stationary body of the surface of Earth, it equals mass x acceleration of gravity. | Weight | 40 | |
| 1248703821 | The precise mathematical shape of a special type of unbound orbit allowed under the force of gravity. | Parabola | 41 | |
| 1248703823 | Law stating that the orbit of each planet about the Sun is an ellipse with the Sun at one focus. | Kepler's First Law | 42 | |
| 1248703825 | Orbits on which an object comes in toward a large body only once, never to return; unbound orbits may be parabolic or hyperbolic in shape. | Unbound Orbits | 43 | |
| 1248703827 | The principle that, in the absence of net force, the total momentum of a system remains constant. | Conservation of Momentum (Law of) | 44 | |
| 1248703829 | The principle that energy (including mass-energy) can be neither created nor destroyed, but can only change from one form to another. | Conservation of Energy (Law of) | 45 | |
| 1248703831 | The combination of speed and direction of motion; it can be stated as a speed in a particular direction, such as 100 km/hr due north. | Velocity | 46 | |
| 1248703833 | The potential energy of mass, which has an amount E=mc^2 | Mass-Energy | 47 | |
| 1248703835 | The principle that, as a planet moves around its orbit, it sweeps out equal areas in equal times. This tells us that a planet moves faster when it is closer to the Sun (near perihelion) than when it is farther from the Sun (near aphelion) in its orbit. | Kepler's Second Law | 48 | |
| 1248703837 | The acceleration of a falling object. On Earth, the acceleration of gravity, designated by g, is 9.8 m/s^2 | Acceleration of Gravity | 49 | |
| 1248703839 | Anything that can cause a change in momentum. | Force | 50 | |
| 1248703841 | A twisting force that can cause a change in an object's angular momentum. | Torque | 51 | |
| 1248703843 | The point at which two or more orbiting objects would balance if they were somehow connected; it is the point around which the orbiting objects actually orbit. | Center of Mass (Of orbiting objects) | 52 | |
| 1248703845 | The product of an object's mass and velocity. | Momentum | 53 | |
| 1248703847 | Energy that an object has by virtue of its position in a gravitational field; an object has more gravitational potential energy when it has a greater distance that it can potentially fall. | Gravitational Potential Energy | 54 | |
| 1248703849 | A satellite that appears to stay stationary in the sky as viewed from Earth's surface, because it orbits in the same time it takes Earth to rotate and orbits in Earth's equatorial plane. | Geostationary Satellite | 55 | |
| 1248703851 | The overall force to which an object responds; the net force is equal to the rate of change in the object's momentum, or equivalently to the object's mass x acceleration. | Net Force | 56 |
