## Physics Midterm Vocabulary

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rachelhorner  on February 1, 2012

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a force is a force, of course, of course!

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# Physics Midterm Vocabulary

 modela pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept
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#### Definitions

model a pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept
system a set of particles or interacting components considered to be a distinct physical entity for the purpose of study
hypothesis an explanation that is based on prior scientific research or observations that can be tested
controlled experiment an experiment that tests only one factor at a time by using a comparison of a control group with an experimental group
accuracy a description of how close a measurement is to the correct or accepted value of the quantity measured
precision the degree of exactness of a measurement
significant figures those digits in a measurement that are known with certainty plus the first digit that is uncertain
frame of reference a system for specifying the precise location of objects in space and time
displacement the change in position of an object
displacement Δx = x(f) - x(i)
average velocity the total displacement divided by the time interval during which the displacement occurred
average velocity v(avg) = Δx / Δt = [x(f) - x(i)] / [t(f) - t(i)]
instantaneous velocity the velocity of an object at some specific instant or at a specific point in the object's path
acceleration the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change
average acceleration a(avg) = Δv / Δt = [v(f) - v(i)] / [t(f) - t(i)]
displacement with constant acceleration Δx = (1/2) [v(i) + v(f)] Δt
velocity with constant acceleration v(f) = v(i) + aΔt
displacement with constant acceleration Δx = v(i)Δt + (1/2)a(Δt)(^2)
final velocity after any displacement v(f)(^2) = v(i)(^2) + 2aΔx
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
Pythagorean theorem c(^2) = a(^2) + b(^2)
tangent function tan θ = opp / adj
sine function sin θ = opp / hyp
cosine function cos θ = adj / hyp
projectile motion the curved path that an object follows when thrown, launched, or otherwise projected near the surface of Earth
vertical motion of a projectile that falls from rest v(y,f) = a(y)Δt
v(y,f)(^2) = 2a(y)Δy
Δy = (1/2)a(y)(Δt)(^2)
horizontal motion of a projectile v(x) = v(x,i) = constant
Δx = v(x)Δt
projectiles launched at an angle v(x) = v(x,i) = v(i) cos θ = constant
Δx = [v(i) cos θ]Δt
v(y,f) = v(i) sin θ + a(y)Δt
v(y,f)(^2) = v(i)(^2) (sin θ)(^2) + 2a(y)Δy
Δy = [v(i) sin θ]Δt + (1/2)a(y)(Δt)(^2)
force an action exerted on an object which may change the object's state of rest or motion
Newton's first law an object at rest remains at rest, and an object in motion continues with constant velocity (that is, constant speed in a straight line) unless the object experiences a net external force
inertia the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction
net force a single force whose external effects on a rigid body are the same as the effects of several actual forces acting on the body
equilibrium the state in which the net force on an object is zero
Newton's second law the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to the object's mass
Newton's second law ∑F = ma
Newton's third law if two objects interact, the magnitude of the force exerted on object one by object two is equal to the magnitude of the force simultaneously exerted on object two by object one, and these two forces are opposite in direction
weight a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe
normal force a force that acts on a surface in a direction perpendicular to the surface
static friction the force that resists the initiation of sliding motion between two surfaces that are in contact and at rest
kinetic friction the force that opposes the movement of two surfaces that are in contact and are sliding over each other
coefficient of friction the ratio of the 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 the product of the component of a force along the direction of displacement and the magnitude of the displacement
net work done by a constant net force W(net) = F(net) d cos θ
kinetic energy the energy of an object that is due to the object's motion
kinetic energy KE = (1/2)mv(^2)
work-kinetic energy theorem the net work done by all the forces acting on an object is equal to the change in the object's kinetic energy
work-kinetic energy theorem W(net) = ΔKE
potential energy the energy associated with an object because of the position, shape, or condition of the object
gravitational potential energy the potential energy stored in the gravitational fields of interacting bodies
gravitational potential energy PE(g) = mgh
elastic potential energy the energy available for use when a deformed elastic object returns to its original configuration
elastic potential energy PE(elastic) = (1/2)kx(^2)
spring constant a parameter that is a measure of a spring's resistance to being compressed or stretched
mechanical energy the sum of kinetic energy and all forms of potential energy
conservation of mechanical energy ME(i) = ME(f)
power a quantity that measures the rate at which work is done or energy is transformed
power P = W / Δt = Fv
momentum a quantity defined as the product of the mass and velocity of an object
momentum p = mv
impulse-momentum theorem FΔt = Δp = mv(f) - mv(i)
impulse the product of the force and the time over which the force acts on an object
conservation of momentum m(1)v(1,i) + m(2)v(2,i) = m(1)v(1,f) + m(2)v(2,f)
perfectly inelastic collision a collision in which two objects stick together after colliding
perfectly inelastic collision m(1)v(1,i) + m(2)v(2,i) = [m(1) + m(2)]v(f)
elastic collision a collision in which the total momentum and the total kinetic energy are conserved
elastic collision m(1)v(1,i) + m(2)v(2,i) = m(1)v(1,f) + m(2)v(2,f)
(1/2)m(1)v(1,i)(^2) + (1/2)m(2)v(2,i)(^2) =
(1/2)m(1)v(1,f)(^2) + (1/2)m(2)v(2,f)(^2)
centripetal acceleration the acceleration directed toward the center of a circular path
centripetal acceleration a(c) = v(t)(^2) / r
centripetal force the net force directed toward the center of an object's circular path
centripetal force F(c) = mv(t)(^2) / r
gravitational force the mutual force of attraction between particles of matter
Newton's law of universal gravitation F(g) = G [m(1)m(2)] / r(^2)
Kepler's first law each planet travels in an elliptical orbit around the sun, and the sun is at one of the focal points
Kepler's second law an imaginary line drawn from the sun to any planet sweeps out equal areas in equal time intervals
Kepler's third law the square of a planet's orbital speed [T(^2)] is proportional to the cube of the average distance [r(^3)] between the planet and the sun, or T(^2) ∝ r(^3)
period and speed of an object in circular orbit T = 2π √[r(^3) / Gm]
v(t) = √(Gm / r)

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