## Astronomy Chapter 4

##### Created by:

mkmoller  on October 11, 2009

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# Astronomy Chapter 4

 momentum =mass x velocity
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#### Definitions

momentum = mass x velocity
astrophysics applies physical laws discovered on earth to phenomena through the cosmos
Newtons second law force = mass x acceleration; amount of acceleration depends on the objects mass and the strength of the net force
Newtons first law an object moves at constant velocity if there is no net force acting upon it; object at rest remains at rest, object in motion stay in motion unless acted upon by another outside force
Newtons third law for any force there is an equal and opposite reaction force
conservation of momentum total momentum of all interacting objects always stay the same
angular momentum "circular momentum" momentum attributable to rotation or revolution. = m x v x r
law of conservation of angular momentum an objects angular momentum cannot change unless it transfers angular momentum to or from another object
law of conservation of energy like momentum and angular momentum energy cannot appear out of nowhere or disappear into nothingness
kinetic energy energy in motion; falling rocks, orbiting planets
radiative energy energy carried by light
potential energy stored energy which might later be converted into kinetic or radioactive energy; rock on edge of cliff
joule standard unit of energy
thermal energy kinetic energy of many particles; collective kinetic energy of the many individual particles moving randomly within substances like a rock or the air or the gas within a distant star
gravitational potential energy depends on its mass and how far it can fall as a result of gravity (more when higher less when lower) (kinetic increases as GPE decrease)
mass energy mass itself is a form of potential energy, e = mc^2 (e potential energy and c speed of light)
Unbound orbits found by newton; paths that bring an object close to another object just once
orbital energy sum of its kinetic energy and gravitational potential energies (always stays the same)
gravitational encounter one way that two objects can exchange orbital energy; they pass near enough so that each can feel the effects of the others gravity
atmospheric drag friction can cause lose of orbital energy
escape velocity speed necessary for an object to completely escape the gravity of a large body such as a moon planet or star; depends on where you start from
spring tides sun and moon tides work together (spring up)
neap tides sun and moon counteract eachother (small)

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