PHYSICS REVIEW
problem
the purpose of the experiment
hypothesis
educated guess to the solution of the problem
independent variable
the factor you change in an experiment that causes a change
dependent variable
the measured variable that depends on the value of the independent variable
conclusion
the answer to the problem written as a statement
K H Dc B D C M
use this chart to convert metric measurements
motion
a change in an object's position
distance
how far an object has moved
displacement
how far an object has moved from its original starting place
instantaneous speed
speed at a given moment
average speed
total distance divided by total time
balanced forces
forces that are equal in size and opposite in direction; they do not move an
object and the net force is equal to zero.
unbalanced forces
forces that are unequal in size and the direction is the same; they cause an
object to move
velocity
the speed and direction of an object's motion; EX: 25 mph North
velocity
5 km/hr upstream
The Law of Conservation of
any time two or more objects interact they may exchange momentum but the
Momentum
total amount of momentum stays the same; momentum is conserved~p=m x v
Newton's 1st Law of Motion
an object in motion stays in motion and an object at rest stays at rest until a
net force acts upon the object
Newton's 2nd Law of Motion
Force= mass x acceleration; the larger something is, the harder it is to move
Newton's 3rd Law of Motion
Forces always occur in pairs; the forces will always be equal and opposite
friction
a force that OPPOSES motion between two surfaces that are touching each
other; it slows down the motion of objects
static friction
friction between two surfaces that are not moving past each other
sliding friction
friction that opposes motion between two surfaces sliding past one another
rolling friction
friction between a rolling object and surface it rolls on
Law of Gravitation
the law that states that the force of gravity depends on the mass and distance
between the objects
gravity
the force of attraction between all things
air resistance
a type of friction that opposes the force of gravity
mass
the amount of matter in an object; stays the same no matter where you are
weight
the force of gravity pulling on a body; changes as gravitational force changes
acceleration of gravity on
9.8 m/s^2
Earth
energy
the ability to cause change
three forms of energy
kinetic, potential, mechanical
kinetic energy
energy in the form of motion; greatest at the bottom of a hill on a rollercoaster
potential energy
stored energy; greatest at the top of a hill on a rollercoaster
three types of potential
elastic (rubber band), chemical (food, fuel), and gravitational (book on a shelf)
energy
thermal energy
the total amount of potential and kinetic energy in a system
Law of Conservation of
Energy may change from one form to another, but the total amount of energy
Energy
never changes
power
the amount of work done in a certain amount of time; the rate at which work is
done; equals work divided by time and is measured in watts
work
the transfer of energy that occurs when a force makes an object move in the
direction of the applied force; measured in joules (lifting weights, moving a
desk)
work NOT being done
holding something over your head, standing still, pushing a wall
mechanical advantage
the number of times a machine multiplies the effort force; not determined the
same for all simple machines, depends on different things
Joules
lever
the unit for energy and work
bar that is free to pivot about a fixed point; ex: seesaws, scissors, baseball
bats, fishing poles, arm, etc.
pulley
grooved wheel with a rope, simple chain, or cable running along the groove
wheel and axle
machine with two wheels of different sizes rotating together
inclined plane
sloping surface that reduces the amount of force required to do work
wedge
inclined plane with one or two sloping sides that pushes things apart
screw
inclined plane wrapped around a cylindrical post
fulcrum
fixed point on a lever; the location of the fulcrum determines the class of lever
1st class lever
fulcrum in the middle; see-saw, wire-cutters, scissors
2nd class lever
fulcrum at the end, load in the middle; wheel barrow, car-jack
3rd class lever
fulcrum at the end, effort in the middle; tweezers, baseball bat
temperature
the average kinetic energy of an object's atoms or molecules
heat
thermal energy that flows from something warm to something cooler
three methods of transferring
conduction, convection, radiation
thermal energy
conduction
direct contact (frying an egg, grilling meat)
convection
currents in liquids or gases (boiling pasta)
radiation
no medium required (sunlight, microwave)
insulator
something that resists the flow of electricity (ex: wood)
conductor
something that allows electricity to flow through it easily (ex: copper)
static electricity
the accumulation of excess electric charges (electrons) on an object
direct current
Electrical current that flows in only one direction through a wire; found in
batteries
alternating current
current in which electrons change direction at a regular rate and is used to run
appliances
resistance
an electrical device that resists the flow of electrical current; measured in
Ohms
voltage
the difference in electrical charge between two points in a circuit; measured in
volts
current
a flow of electricity through a conductor; measured in amperes
Ohm's Law
I=V/R
series circuit
a circuit in which the objects are connected in a single path (holiday lights)
parallel circuit
circuit in which electric current can follow more than one path (house sockets)
magnetic force
interaction between two magnets - like poles repel and unlike attract
magnetic pole
the regions of a magnet where the magnetic force exerted by the magnet is
strongest
magnetic domain
groups of atoms with aligned magnetic poles
electromagnetism
the connection between electricity and magnetism; magnetism produced by an
electric current
electromagnet
temporary magnet made by passing an electric current through a wire coiled
around an iron bar
nuclear fission
the process of splitting a nucleus into two nuclei with smaller masses
nuclear fussion
the process of two nuclei with low masses combining to form one nucleus of
larger mass
wave
repeating disturbance or movement that transfers energy through matter or
space
mechanical wave
waves that must travel through a medium
electromagnetic waves
waves that do not require a medium to travel through
transverse waves
matter in the medium moves at right angles to the direction the wave travels;
made of crests and troughs
compressional waves
matter in the medium moves back and forth in the same direction the wave
travels; made of compressions and rarefactions
rarefaction
less-dense region of compressional waves
compression
dense region of compressional waves
reflection
when a wave strikes an object and bounces off
refraction
the bending of a wave caused by a change in its speed as it moves from one
medium to another
interference
when two or more waves overlap and combine to form a new wave
diffraction
when an object causes a wave to change direction and bend around it
amplitude
measure of energy carried by a wave
wavelength
distance between one point on a wave to the nearest point like it (crest to
crest; compression to compression)
crest
highest point of a transverse wave
trough
lowest point of a transverse wave
doppler effect
change in the apparent frequency of a wave as observer and source move
toward or away from each other
opaque
absorbs and reflects light; does not allow light to pass through it
translucent
some light passes through it
transparent
almost all light passes through it
law of reflection
the angle of incidence is equal to the angle of reflection
neon lights
glass tubes filled with neon that produce light from electron collisions
fluorescent lights
When an electric current is passed through a tube, gas inside emits ultraviolet
waves that cause a powder to glow
mirror
allows the reflection of an object to be seen; either a virtual or real form
lens
transparent material with a curved surface that refracts light rays
convex lens
a curved lens in which the center is thicker than the edges so it converges light
to the focal point
concave lens
a lens that is thicker at the edges than in the middle that bends light rays away
from one another
convex mirror
a mirror that is curved outward like the back of a spoon; diverges to the focal
point
concave mirror
a mirror that is curved inward like the inside of a spoon; converges to the focal
point
constant
the parts of an experiment that stay the same
watt
the unit for power