free fall equation
1/2 at^2
the law of inertia
every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted upon it.
a force can be described as ...
a push or a pull
measure of inertia
mass
net force
the combination of all forces acting on an object.
in what direction to objects move relative to net force?
objects move in the direction of net force.
when net force is zero, an object is said to be in..
equilibrium.
objects in equilibrium have their weight exactly balanced by...
a "support force" / "normal force
acceleration is caused by
force (net force)
acceleration is proportional to
net force. a = f /m. (newton's second law)
acceleration is inversely proportional to
mass.
friction resists
acceleration
terminal velocity
the speed at which the acceleration of a falling object is zero because friction balances the weight,
at terminal speed the force of air resistance balances the force of gravity
whenever one object exerts a force on a second object..
the second object exerts an equal and opposite force on the first object.
action / reaction pair,
switch the noun but the verb stays the same
forces are ______ in an action/reaction pair
equal
accelerations are _______ in an action/reaction pair
different (because masses are different)
momentum(p) =
mass x velocity
momentum is
inertia in motion.
momentum is changed by..
impulse. (internal forces DO NOT change momentum)
impulse =
force x time (or change in momentum)
bouncing
impulses are greater when something bounces because a force is needed to stop the object and to set it in motion once more
conservation of momentum
if no net force or net impulse acts on a system, the momentum does not change
elastic collisions are
bouncy collisions" ; two objects collide without being permanently deformed and without generating heat.
( total p before = total p after )
( Pa + Pb = Pa1 + Pa2 )
inelastic collisions are
sticky collisions" ; two objects collide and become distorted, coupled together, and generate heat.
( total p before = total p after )
( Pa + Pb = Pboth )
work is..
the middle step between transferring energy from one object to another.
work (w)=
w = fd
( or change in energy )
power(p) =
work / time
Potential energy(pe) =
pe = mgh
potential energy is a
form of mechanical energy.
potential energy is due
to the position of an object
Kinetic energy(ke) =
1/2mv^2
kinetic energy is a
form of mechanical energy
kinetic energy is due to
the speed of an object
important KE note !
the kinetic energy of an object is equal to the work required to bring an object to that speed from rest, or the work the object can do while being brought to rest.
if the speed of an object is doubled, its kinetic energy
quadruples
conservation of energy
energy cannot be created or destroyed. it can be transformed from one form into another, but the total amount of energy never changes.
simple machines
Win = Wout ; Work in = Work out
(On an inclined plane)
work in = distance up incline x force it takes
work out = distance straight up x force it takes
actual mechanical advantage AMA
Fout / Fin
theoretical mechanical advantage TMA
Din / Dout
(On an inclined plane)
distance in = length of plane
distance out = height
(On a lever)
distance in = is the length from your push/pull to the fulcrum
distance out = is the length from the object to the fulcrum
pulley TMA
number of strings
simple machines cannot _____
increase work
simple machines can increase _____
force at the expense of distance, or distances at the expense of force
efficiency =
AMA / TMA
every atom has a..
positively charged nucleus surrounded by negatively charged electrons
an atom's nucleus is composed of protons and neutrons. Protons have _______
positive charge
electrons have ______
negative charge
neutrons have ______
no charge
A neutron is what size compared to a proton?
BIGGER
A proton is what size compared to an electron?
BIGGER
Like charges..
repel
opposite charges...
attract.
A charged atom is called
an ION.
Atoms are charged only by the movement of
electrons. protons do not move
Charge cannot..
be created or destroyed. it can only be moved from one object to another
Electric charges move better in...
Conductors
Electric charges move poorly in...
Insulators
Electric force,
there is an electric force between any two charged particles.
Electric charging: Charging by Contact
A charged object is brought near a neutral one, some of the electrons from the charged object want to jump to the neutral object because like charges repel.
Electric charging: Charging by Friction
When two objects rub against each other, electrons jump from one object to another.
Electric charging: Charging by Induction and Grounding
A charged object is brought near a neutral one. The electrons in the neutral object want to get as far away from the charged object, because like charges repel. If the electrons are given a path out of the neutral object, they will take it. This will leave the formerly neutral object with a positive charge.
Causes of attraction:
opposite charges, charge separation, polarization
polarization
hold an object of a certain charge near an object where the electrons and protons cannot move too much just on opposite sides of the item
Every electric charge is surrounded by an electric field that has both
magnitude and direction
Electric field lines point in the direction that:
that a positive charge would go. (positive, out negative in)
electric potential is the same thing as
voltage.
electric potential =
EPE / charge
A charge has electric potential after..
after work is done on it to move it in a direction it is not inclined to go in.
charge flows when...
there is a potential difference
batteries work to create a...
constant potential difference
Electric Current is
the flow of Electric Charge, measured in coulombs/second
current is caused by..
voltage difference.
current is dangerous,
not voltage.
CURRENT =
I = V / R
Electric power:
the rate at which energy is transformed from one form to another
in order for a bulb to light, electrons must have a..
complete path through battery and bulb.
A circuit:
any path along which electric current flows
Series Circuits
only one path goes through the circuit. if one bulb goes out, the whole thing goes out.
resistance in series circuit:
equal to sum of all resistors
current in series circuit:
same in each component
voltage in series circuit:
not the same
Adding resistors in series:
lowers current.
Parallel Circuits
each bulb has its own path from the battery, if one burns out others will stay lit
Voltage in a parallel circuit
same throughout entire circuit
Total current in parallel
equal to sum of currents in each branch.
Adding resistors in parallel
increases curent
TOTAL RESISTANCE IN PARALLEL;
1/R = 1/R1 + 1/R2
Every magnet has both a
north and south pole.
Like poles..
repel
opposite poles...
attract.
All moving electric charges are surrounded by..
magnetic fields.
A magnetic field is produced by..
motion of electric charge
Magnetic field lines OUTSIDE magnet..
North to South
Magnetic field lines INSIDE magnet..
South to North
Every spinning electron is a
tiny magnet !
Domain
cluster of aligned atoms
The alignment of domains produces
a magnet.
In a magnet, domains are aligned with a..
magnetic field
The magnetic field lines surrounding a current carrying wire form..
concentric circles !
When current in magnetic field lines reverse direction,,,
the direction of the magnetic field also changes.
A wire carrying current is an
electromagnet
Magnetic field intensity increases as
number of loops increases
Magnetic field intensity increases when a piece of iron is put in a coil because
the domains align with the magnetic field
A charged particle at rest in a magnetic field will not..
will not feel a force
A charged particle moving in a magnetic field will..
will feel a force
A charged particle moving in a magnetic field feels NO force when it is moving ________ to the magnetic field.
parallel
A charged particle moving in a magnetic field feels THE STRONGEST force when it is moving ________ to the magnetic fied
perpendicular
The force experienced by a moving charged particle in a magnetic field is always...
perpendicular to the motion of the charged particle and magnetic field lines.
ElectromagneticInduction: Voltage and current can be induced in a wire by..
the movement of the wire in the magnetic field, because A CHANGE IN THE MAGNETIC FIELD PRODUCES CURRENT
The induced voltage in a coil is proportional to..
the number of loops.
Induced voltage is heightened by..
quicker motion of the wire through the magnetic field.
Induced voltage is directly proportional to..
the number of loops.
Generators are the opposite of
motors.
generators change..
mechanical energy into electrical energy.
Generators produce:
alternating current.
A transformer with more loops on secondary than primary coil is:
step up.
A transformer with more loops on primary than secondary coil is:
step down.