Alevel physics Flashcards
free fall in air.
at time 0, only weight is acting, acceleration is g, then speed increases, so drag increase, so resultant decrease, so decreasing acceleration, then drag is equal weight, fr is 0. reaching terminal velocity, then. drag greater than weight, deceleration
describe x axis motion in projectiles
no force, only weight, constant horizontal motion, speed is distance over time
describe y axis
constant acceleration, y component changes, use 5 acc rules, up positive, down negative
what is rule of force
mass. times acceleration
when is a body equilibrium
resultant force AND resultan moment is 0
what is inertia
the tendency of object to reset change in state of rest or uniform motion
what is mass
measure of inertia// amount of matter in body
what is first law
object remains equilibrium unless a resultant force is acting on it
newtons second law
force is the rate of change in momentum
newtons third law
when 2 objects interact, for every action thee is an equal and opposite reaction
what is momentum
mass times velocity
impulse
mv-mu, or ft
why use softer material\l in crashing
time increases to crash so force decrease so safer
law of. conservation of momentum
before equal after, m1u1 and m2u2 is equal to m1v1 plus m2v2
what do to with 2d collision.
each axis separately then simultaneous
what’s the check for elastic collision
u1-u2=v2-v1
types of forces
tension, friction, drag, upthrust, weight, normal contact
proof of conservation of momentum
force is rate of. change in momentum, when time is same, momentum. before. collision is ewualnbut opposite to collision after
whats center of gravity
point where whole body is considered to act.
whats moment
force times perpendicular distance
when is max moment?
when. angle is 90 DEGREE
whats a couple
2 forces equal and opposite act. on 2 different points. causing object to rotate
pressure
force/ area or ugh
total pressure?
atm 100000 plus pgh
upthrust
pg VOLUME
how do gases exert pressure
gas molecules collide with walls, change in direction, change in momentum, change is momentum is force, pressure is force over area
why pressure decreases. at high altitude
temp decreases so less collision, less pressure, AND height column decreases, so less pressure
whats work done
force tumes PARALLEL distance OR pressure times change in. volume of gas
gravitational potential energy
energy stored in any mass in gravitational field MGH
elastic potential energy
energy stored in object when its twisted, stretched
electric. potential
energy stored in charge released
to electric field
kinetic energy
energy possessed due to motion, HALF M V SQUARED
PROOF OF KINETIC EQUATION
v2 is u2 +2as where u is 0, s subject, wd is fd, ma x s
whats the universal rule
energy start +wd for object-wd against object = ENERY FINAL
whats power
energy per time OR force times velocity
efficiencyofpower
out/in x100
whats stress
force per area
whats strain
fractional change in length
whats ultimate tensile stress
max stress wire can support before breaking
hookes law
force and extension directly proportional up to limit of proportionality, f=kx
whats limit of proportionality
end point of direct proportionality
elastic limit meaning
point beyond where material is perpenantly deformed
spring in series
x is doubled
spring in parallel
x is halved
young modulus E
stress / strain
equation for young
FLEXA///KL/a
YOUNGS MODULUS FOR
rubber 1x107, copper 1.3x1011
steel, 2.1x1011
elastic potential equation
1/2fx, 1/2kx2
elastic energy density
elastic energy/volume OR 1/2 stressxstrain
whats electricity
flow of charges thru conductor
electric current
rate of flow of charges//Q/T
another equation fir TOTAL CHARGE
number of electrons x 1.6x10 power -19
free electron number density
metal 10 power 28
semi conductor 10 power 23
equation for total number of electrons in wire
n X volume// NAL
equation for total charge
N AL W
EQUARION FOR CURRENT
NEVA
emf meaning
total energy gained per unit charge in battery converted from chemical to electric
pd meaning
total energy lost per unit charge in battery converting electric energy to other forms
volt
energy per charge
ohms law
at CONSANT TEMPERATURE, I and v are directly prop
why resistance occurs
free moving electrons collide with positive ions, collisions cause loss electric energy
metalic conductor
slope is 1/r
filament lamp
curves towards V
thermistor
temp inc resistance dec
why thermistor inversely prop
when temp increase, electrons Gain enough energy to free themselves so resistance decrease
impure metal and resistance
impure metal have higher resistance
than pure metals
resistance other equation
PL/A
Power in electricity
IV, I2R, V2/R
HOW TO CALCULATE ENERGY
calculate power first using iv, then energy using ENERGY EQUALS POWER TIMES TIME
CONVERSION OF KWH TO JOULES
1kwh = 3.6x10 power 6
1MV TO JOULES
1MV= 1.6X10 POWER -13
what happens when resistance is very high
max terminal volt,
when is power max
external resistance is equal to internal resistance
what happens when resistance increase
current decrease, terminal volt. increase and lost volt decrease
why connect battery in parallel
less power loss, longer life
volt and kda dkda
EMF= VLOST PLUS TERMINAL
POWER LOSS AD=ND CROSS SECTION
ass area decreases, resistance increase so more pd, so more power loss
