Chapter 3: Gravity, Force, and Space Flashcards
weight
the force of gravity acting on mass
the force of gravity obeys
an inverse square law
(when the distance increased by a factor of 3, the force becomes 9 time weaker
LEO: low-earth orbit
the satellite moves at 8 kilometers per second and orbits the Earth in 1.5 hours
useful for Earth observation, including spying
Geosynchronous satellites
useful for application where the position of the satellite must stay fixed with respect to the ground
MEO: medium-earth orbit
GPS
a GPS receiver determines its location by measuring the distance to three or more of these satellites
acceleration can be measured in
g
g-rule
to accelerate an object to 10 g requires a force 10 times as great as that object’s weight on the Earth’s surface
Newton’s 2nd law
black hole
objects whose escape velocity exceeds the speed of light
conservation of momentum
when a gun is fired, the bullet goes forward and the gun goes backward
halving rule
the pressure drops by a factor of 2 every time your increase your altitude by 5.5 kilometers
angular momentum
a momentum that applies to circular motion
e.x. hurricanes, tornadoes, drains
if gravity were turned off
satellites would move in straight lines rather than in circles
to escape to space completely requires an energy of
15 Cal/g
Newton’s three laws
1 st: an object in motion tends to stay in motion unless there is an outside force
2 nd: F = ma
3 rd: 力的作用是相互的
Astronauts in the ISS
would fall to the Earth if something were to slow their velocity perpendicular to the Earth.
are falling “around” the Earth.
