chapter 7
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
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there is a gravitational attraction between any two masses in the universe. The strength of the force is inversely proportional to the distance squared
newtons law of universal gravitation
F~ mass1 X mass2 ——————- distance squared
newtons law of universal gravitation
related the intensity of an effect to the inverse square of the distance from the cause
inverse square law
one example of inverse square law
A light that is three times farther away, will only be 1/9 as bright
Spring tides
higher than average high tides in lower than average low tides. Occurs when sun, moon, and earth are in line. Strongest during new moon and full moon
neap tides
lower than average high tides, and higher than average low tides. First and third quarter
velocity parallel to the earth’s surface
trangential velocity
all the matter in the universe was compressed into a small ball that exploded. this expanding material gave rise to current stars and galaxies
Big Bang theory
matter that can’t be seen but exerts a gravitational pull on stars and galaxies
dark matter
any object that moves through the air or space under the influence of gravity
projectile
the curved path of a projectile caused by both horizontal and vertical motion
parabola
what angle must projectiles must be thrown at to travel the fastest
45
slows down objects traveling at high speeds
air drag
an object in orbit around a body with a larger mass
satellite
the earth drops a vertical distance of 5m for every 8000 m tangent to its surface
curvature of the earth
an oval path based on 2 fixed points called foci
ellipse
a special kind of ellipse, both foci are at the same point
circle
the speed that a projectile must reach in order to escape the gravitational attraction of the the earth
escape speed