59 terms

This set covers Abeka Physics Chapter 8: "Forces in Nature" (pages 110-129).

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

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)