models
a pattern, plan, representation designed to show the structure of an object, system or concept
hypothesis
reasonable explanation for observations that can be tested
controlled experiment
an experiment that tests only one factor at a time using a comparison of a control group with an experimental group
accuracy
description on how close a measurement is to the correct value of the quantity measured
system
a set of particles or interacting components considered to be a distinct physical entity for the purpose of study
precision
degree of exactness of a measurement
significant figures
digits in a measurement that are known with certainty
frame of reference
a system for specifying the precise location of objects in space and time
displacement
the change in position of an object
average velocity
total displacement divided by the time interval during which the displacement occurred
instantaneous velocity
velocity of an object at some instant or at a specific point in the object's path
acceleration
rate at which velocity changes over time
free fall
the motion of a body when only the force due to gravity is acting on the body
scalar
a physical quantity that has magnitude but no direction
vector
a physical quantity that has both magnitude and direction
resultant
a vector that represents the sum of two or more vectors
components
the projections of a vector along the axes of a coordinate system
projectile motion
the curved path that an object follows when thrown or projected near the surface of earth
force
an action on an object which may change the objects state of rest or motion
contact force
forces that involve physical contact
field force
does not involve physical contact between two objects
inertia
tendency of an object to resist being moved
net force
single force whose external effects on a body are the same as the effects of several forces acting on that body
equilibrium
state in which the net force on an object is zero
weight
measure of the gravitational force exerted on an object
normal force
force that acts on a surface in a direction perpendicular to the surface
static friction
force that resists the initiation of sliding motion between two surfaces that are in contact and at rest
kinetic friction
force that opposes the movement of two surfaces that are in contact and are sliding over each other
coefficient of friction
ratio of magnitude of the force of friction between two objects in contact to the magnitude of the normal force with which the objects press against each other
work
amount of energy transferred by a force acting through a distance.
kinetic energy
energy of an object that is due to the objects motion
work kinetic energy theorem
net work done by all the forces acting on an object is equal to the change in the objects kinetic energy
potential energy
energy associated with an object because of the position, shape or condition of the object
gravitational potential energy
the potential energy storied in the gravitational fields of interacting bodies
elastic potential energy
energy available for use when a deformed elastic object returns to its original configuration
spring constant
a parameter that is a measure of a springs resistance to being compressed or stretched
mechanical energy
sum of kinetic energy and all forms of potential energy
power
a quantity that measures the rate at which work is done or energy is transformed
momentum
a quantity defined as the product of the mass and velocity of an object
impulse
product of the force and the time over which the force acts on an object
perfectly inelastic collision
a collision in which two objects stick together after coinciding
elastic collision
a collision in which the total momentum and the total kinetic energy are conserved
centripetal acceleration
the acceleration directed toward the center of a circular path
gravitational force
mutual force of attraction between particles of matter
torque
quantity that measures the ability of a force to rotate an object around some axis
lever arm
perpendicular distance from the axis of rotation to a line drawn along the direction of the force
Newtons law of gravity
all masses are attached to one another.
period
time required for one cycle to pass a given point.