1.
dwarf planet: a celestial body that's...
a) in orbit around the Sun
b) is nearly round
c) has not cleared the neighborhood around its orbit
2.
gravity: a force of attraction between two objects; the strength of the force is due to the mass and distance between the two objects
3.
high tide: a tide that reaches maximum height for a given part of the day
4.
inertia: the tendency of an object to remain either at rest or in motion unless acted on by an outside force
5.
Law of Inertia: law stating that a body in motion tends to travel in a straight line unless an outside force disturbs it
6.
Law of Universal Gravitation: law stating that any two objects in the universe have gravity and will attract each other, and that attraction depends on how much mass each object has and their distance from each other
7.
low tide: a tide that reaches minimum height for a given part of the day
8.
mass: the total amount of matter in an object; not dependent upon gravitational pull
9.
neap tide: lower-than-normal high tide that occurs when the first or third quarter moon, Earth, and the Sun are at right angles to each other and the gravitational force of the Sun partially offsets the gravitational force of the Moon
10.
orbital period: the time that it takes an object to orbit another object one complete time
11.
orbital velocity: the speed of an object as it travels in an orbit around another object
12.
spring tide: higher-than-normal high tide during the month that normally occurs during a new and full moon when the Sun, Moon, and Earth are in line and their gravitational forces are combined
13.
tide: periodic rising and falling of the surface level of an ocean and other waters resulting from the gravitational attraction of the Moon and the Sun on the solid and liquid surfaces of Earth
14.
velocity: speed and direction that an object travels over a specified distance during a measure amount of time; rate of motion
15.
weight: a measure of the force of gravity on an object
