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Abeka Physics Chapter 8
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Gravity
This set covers Abeka Physics Chapter 8: "Forces in Nature" (pages 110-129).
Terms in this set (59)
Principia Mathematica
book by Isaac Newton that presented three laws of motion that still serve as the conceptual foundation of physics
inertia
term for a body's tendency to maintain its velocity, or a resistance to any change in velocity
straight line, speed
A body in motion tends to move in a ____ ___ at a constant ____.
force
term for any push or pull on an object
force
A body at rest tends to stay at rest, unless acted upon by an outside ___.
friction
term for the force that acts against every object in motion in the opposite direction to slow it down, or the resistance arising when an object moves through a medium or across a surface
Newton's first law of motion
the law that states that a body in motion tends to move in a straight line at a constant speed, and a body at rest tends to stay at rest, unless acted upon by an outside force
F = ma
equation for Newton's second law of motion
inertial mass
term for rest mass
weight
term for the force exerted on an object's mass by the earth's gravity
Fw = mg
equation for weight
Newton's third law of motion
law that states that every action has an opposite and equal reaction
pairs
Forces always occur in action-reaction ____.
line
Action and reaction are always opposite, equal, and along the same ___.
Motion
____ is caused by unbalanced forces acting on the same object.
static friction and kinetic friction
two types of friction
kinetic friction
term for an object's resistance to sliding
static friction
term for an object's resistance to start sliding
False
True or False:
Kinetic friction
is dependent on the area of contact between the surfaces.
False
True or False:
Kinetic friction
is dependent on velocity.
weight
Kinetic friction
on a horizontal surface is proportional to the ____ of the moving object.
normal force
term for the force of a surface against the weight of an object
perpendicular
The normal force always acts _____ to a surface.
True
True or False:
Rough
surfaces produce
more
friction than smooth surfaces.
bearing
term for any part of a machine that supports a moving part
minimizing roughness; choosing suitable materials; lubricating; and rollers and bearings
four methods of reducing friction on a surface
strong force, electromagnetic force, weak force, and gravitational force
the four fundamental forces of nature (from strongest to weakest)
strong force
the strongest of the four fundamental forces that holds an atomic nucleus together
electromagnetic force
the fundamental force that exists only between electrically charged bodies, binds the electrons of an atom to the nucleus, and causes an atom to resistance the penetration of its space by another atom
weak force
the fundamental force responsible for certain particle interactions in the radioactive decay of atomic nuclei
gravitational force
the weakest of the fundamental forces that exists between any two bodies of matter; attracts, but does not repel; and holds the moons, planets, and stars in their orbits
electromagnetic force and weak force
two fundamental forces that might be basically different expressions of the same force
geocentric
term that means "earth-centered"
Ptolemy
Greek astronomer who created a geocentric model of the solar system in the second century A.D.
heliocentric
The _____ ("sun-centered") model of the solar system has become the foundation of modern astronomy.
Nicolaus Copernicus
sixteenth century Polish astronomer who proposed that sun was the center of the solar system
law of orbits, law of areas, and law of periods
Johannes Kepler's three laws of planetary motion
law of orbits
law that states that the orbit of every planet has the shape of an ellipse and that the two foci of each planetary orbit are relatively close together
law of areas
law that says that as a planet gets farther away from the sun, the distance traveled by the planet must shorten and the velocity must decrease
aphelion
term for the farthest position from the sun in a planet's orbit
perihelion
term for the closest position to the sun in a planet's orbit
period
term for the time required for any planet to complete one orbit about the sun
law of periods
law that says that for any planet, the square of the period of revolution is proportional to the cube of the average distance from the sun
kinematics
term for the science of mechanics that seeks merely to describe motion by describing its causes
dynamics
term for the science of mechanics that seeks to explain motion by describing its causes
universal law of gravitation
law that states that the same kind of force exists between any two masses, regardless of size; specifically, that they are mutually attracted by a force governed by the proportionality
gravitation
term for the attractive force that exists between any two masses
True
True or False: 'Gravitation' and 'gravity' do
not
mean the same thing.
gravity
As the
distance
from the earth's center of mass
increases
, ____
diminishes
.
static equilibrium
An object that remains at rest within earth's gravitational field is said to be in ____ _______.
center of gravity (CG)
term for the one spot that represents the combined effect of gravity's influence on all the particles in an object
stable equilibrium
An object in ____ _____ is not easily tipped over.
unstable equilibrium
An object in ____ _____ is upset at the slightest disturbance.
neutral equilibrium
An object in ____ _____ can be overturned without changing the height of its center of gravity.
instability
term for the state in which an object's center of gravity is unsupported, and the point where the force of gravity is effectively applied is free to move in the direction of the applied force
multiple suspensions
the simplest way of determining the center of gravity for irregular objects
center of mass
term for the point in an object that describes the combined effect of all the individual particles of mass
gravitational field
Scientist have sought to remove the mystery from gravitation by imagining that each object sets up a _____ ____ in which other objects are impelled to move by a force in the object's surrounding space.
gravitational field strength
term for the acceleration of an object in free fall (the gravitational force per unit mass)
;