# Physics P2A

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Resultant force [3]
equal and opposite force / overall force determines whether it accelerates/stopsetc. / accelerates in direction of greater force
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Acceleration
how fast velocity is changing and speed with direction specified
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Veloicty- the graph - gradient =
acceleration
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flat section on velocity time graph
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Frcition [3]
opposite direction / 2 surfaces in contact / object passing through fluidd = drag
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reducing drag
keep shape of object streamlined - DRAG INCREASES AS SPEED INCREASES
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Terminal velocity
initially accelerate due to force of gravity, eventually resultant force will be zero due to the increased air resistance which increases as speed does and object will fall at STEADY SPEED
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Parachute example of Terminal velocity
much more air resistance with same force pulling him down (weight) upward force increases greatly so so person slows down RAPIDLY due to large surface area of parachute. Forces become equal and theres a lower terminal velocity
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Parachute terminal velocity on a velocity time graph [6]
accelerating quickly to ground // upward force increases due to large speed // forces are balanced = steady speed // parachute opes and slow down// equal forces// hits ground
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what is work done
energy transferred e.g. stretching squashing releasing
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elasticity forces
force acting on object causes change in shape of object // e.g. force applied to spring = stretching and storing EPE// EPE is stored when work is done to change its shape // Extension is directly proportional to force applied // if limit O P not exce
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what is limit of proportionality
spring doesn't return to normal shape once released. OVER STRETCHING spring - stays overstretched - can't be proportional
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Power
rate of doing work powerful = transferring lots of energy in short amount of time
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Earth and moon GFS
EARTH = 10N MOON = 1.6N
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GPE space shuttle example [3]
lots of kinetic energy and friction // kinetic to heat energy transferred // LOTS OF ENERGY TRANSFERRED
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What is gravitation potential energy //GPE
energy an object has by virtue of its position in a gravitational field
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object raised vertically =
work done AGAINST gravitational force SO OBJECT GAINS GPE
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What does kinetic energy depend on
mass and speed
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what is weight
force that depends on gravitational field strength which depends on where u are in the universe
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Momentum [3]
property of moving objects - vector quantity as it has size AND DIRECTION // greater mass and velocity = greater momentum // closed system momentum before= momentum after (conservation of momentum)
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how to calculate momentum
1. momentum of p1 and p2 (mass x velocity) // 2. add together for total momentum // 3. add masses tether and use formula
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Crumple zones [3]
longer impact time // more impact time reduced // kinetic energy converted into other forms as it changes shape
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Seat belt [3]
the stretch increases impact time for wearer to stop // reduces forces acting on chest // some kinetic nrgy is absorbed by stretching
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air bags [3]
slows you down // reduces force // prevent hitting hard surfaces
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side impact bars
direct kinetic energy to other parts (away from passenger)
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what happens when you apply the breaks
kinetic energy goes to heat energy due to FRICTION OF BRAKE AGAINST WHEEL
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Thinking distance
distance moved by car as driver is reacting
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Total stopping distance
thinking + stopping distance
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braking distance
stance travelled between applying breaks and coming to full stop
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faster car travels =
longer stopping distance and bigger breaking distance needed
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Thinking distance
tiredness drugs alcohol
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braking distance
wet icy road / worn tires/brakes faulty brakes
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Static electricity -
certain insulating materials rubbed together = electrically charged
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static electricity negative and positive charge
negatively charged electrons are rubbed off on one material GAIN = NEGATIVELY CHARGED LOSE ELECTRONS = POSIITVELY CHARGED
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Insulating materials -
plastic / polythene
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prices of static electricity
electrons are transferred and theres an imbalance of electrons = overall charge? Static elec caused by movement of electrons from one to another
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voltmeter
measures voltage / P.D.
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Ammeter
measures current in amps
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open switch
NO CURRENT CAN FLOW
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Fixed resistor
lowers current
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VRIABLE RESISITOR
Obtains orange of P.D. values
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Thermistor [4]
increase temp = lower resistance because higher current can flow // cool temp = resistance rises // thermostats/incubators/homes
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LDR [4]
higher light intensity = lower resistance due to the high current flowing // lower light = higher resistance // depends on intensity of light // automatic night lights and burglar detectors
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LED
CURRENT CAN ONLY FLOW ONE WAY FORWARDS // indicated presence of current // used for lighting bc uses much smaller current // TVs , Clocks , Traffic lights N remote controls
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Potential difference
work done / energy transferred per coulomb of charge -------- increases as current increases DIRECTLY PROPORTIONAL
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current
flow of electric charge
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what peens on size of electric current
RATE of flow of electric charge
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Total resistance =
sum of all individual resistors / components
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total p.d. of cell
sum of all individual CELLS
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Current in series [4]
current is the same // pd is shared between components // total pd = sum of individual cells //
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Components in parallel [3]
pd is same, current diff in diff branches // total current = sum of current in diff compenmets
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Different resistors graphs
diff slopes due to diff resistors // constant temp // current is proportional to p.d.
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Filament lamp
as temp of filament increases, resistance increases hence wiggle curve q
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Diode graph [2]
v high resistance in app direction // current only flows through diode in one direction
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Raise temp on metal [3]
atoms gain energy and vibrate more risibly - electrons collide more frequently and due to increased collisions current gets lower
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## Other cards in this set

### Card 2

Acceleration

#### Back

how fast velocity is changing and speed with direction specified

### Card 3

#### Front

Veloicty- the graph - gradient =

### Card 4

#### Front

flat section on velocity time graph

Frcition [3]