Physics 2
- Created by: pheegrace
- Created on: 24-03-16 20:05
What is a resultant force?
overall force on a point or object
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If there is no resultant force, how is a vehicle moving?
at constant speed
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If there is 0 resultant force, how is a vehicle moving?
it isnt, its stationary
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If it has a non 0 resultant force, how is the vehicle moving?
accelerating or deccelerating
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When two vehicles interact what forces do the exert on eachother?
equal and opposite, affected by mass of objects involved
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What is air resistance and what does it do?
friction - slows things down
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If the driving force is 1000N and the air resistance is 600N, what is the resultant force?
1000-600=400N
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What is terminal velocity?
Max speed
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What is the stopping distance?
distance covered from spotting a hazard to completely stopping
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How is stopping distance calculated?
thinking distance + braking distance
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What is thinking distance affected by?
how fast you are going and how dopey you are
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What is braking distance affected by?
how fast you are going, how good your brakes are, how good your tyres are and how good the grip is on the surface
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What is speed?
how fast - 30mph
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What is velocity?
how fast and direction - 30mph north
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What does the line mean on a distance-time graph?
gradient=speed, flat=stationary, /or\=steady speed, \=back to start point, steepening curve=speeding up, levelling off curve=slowing down
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What does the line mean on a velocity-time graph?
gradient=acceleration, flat=steady speed, steeper=greater acceleration/decceleration, /=acceleration, \=deceleration, area under=distance, curve=changing acceleration
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What is acceleration?
how quickly the velocity is changing - change in direction - change in speed - both
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What happens when a force moves an object through a distance?
energy is transferred and work is done (J)
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What is gravitational potential energy?
energy an object has because of its vertical position in a gravitational field
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What is kinetic energy?
anything moving
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What happens to an objects GPE when it is falling?
It turns into kinetic energy (some heat and sound)
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What is extension directly proportional to?
load or force applied
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What is the limit of proportionality?
the max force that an elastic object can take and still extend proportionally
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What happens if you increase the force past the limit of proportionality?
the object will be permanently stretched - when the force is removed, the object will be longer than at the start
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What is weight?
caused by the pull of gravity (N)
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What is mass?
same value anywhere is universe, amount of 'stuff' in an object (kg)
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What is gravity?
makes things accelerate towards ground, gives things a weight
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What is power?
rate of energy transfer
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What is the conservation of momentum?
momentum before=momentum after (collision)
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With greater mass and greater velocity this makes the momentum...
greater
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What is static electricity?
+ and - electrostatic charges produced by movement of electrons, caused by friction, electrical charges move easily through conductors
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What is current?
flow of electrical charge, only flow if p.d across component
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What is resistance?
anything in circuit which slows flow (ohms) (graphs in revision guide)
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If there is greater resistance across a component the current that flows is...
smaller
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What is potential difference/p.d.?
work done per coulomb of charge, driving force that pushes current round
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What is an ammeter?
measures current, in series
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What is a volmeter?
measures p.d., in parallel around component
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What is a variable resistor?
alters current flowing through circuit
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What is a diode?
let current flow freely in one direction but not in the other
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What is an LDR?
dependent on light intensity, bright light=resistance falls, auto outdoor lights
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What is a thermistor?
temp dependent, hot=resistance drops, car engine temp sensors
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What is LED?
emits light when current flows through in forward direction, used in tv to show when switched on
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What is a series circuit?
components are connected in a line so if the circuit breaks they all stop
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In series - how can we work out the p.d of the supply?
add the p.d of the components, p.d is shared across components
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In series - the current is...
the same through the whole circuit
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In series - how can we work out the total resistance?
add up all the resistances through the circuit
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What is a parallel circuit?
each component is seperately connected so disconnecting one will hardly affect others
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In parallel - the voltage/p.d across the components is...
the same
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In parallel - the total current is...
equal to the total of all the currents through the seperate components
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What is AC?
alternating current - constantly changing direction (uk mains supply)
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What is DC?
direct current - flows in the same direction (cells and batetries)
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What is an oscilloscope and what does it show for AC or DC?
snazzy voltmeter. AC = ~ voltage is vertical height DC = - volatage is straight line to centre line
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What is the blue wire?
neutral - allways 0volts, electricity flows in and out
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What is the brown wire?
live - alternates between high + and - voltage, electricity flows in and out
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What is the green and yellow wire?
earth - protects wiring and for safety, attatched to metal case and carry electricity to the earth if something goes wrong and live or neutral touch metal casing
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What is a fuse for?
a surge in the current will melt the fuse when amount of current is greater than fuse rating which cuts off live supply and breaks circuit
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What is a circuit breaker?
detect surge in current and open switch to break circuit, easily reset so more convenient than fuses however are more expensive
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What is an isotope?
different form of the same element, same protons different neutrons, same atomic number different mass nuber
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When does radioactivity happen?
randomly
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What are sources of background radiation?
51% radon gas, 10% cosmic rays, 14% rocks and building materials, 1% nuclear industry, 12% medical x-rays, 12% food
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What is an alpha particle?
helium nucleus - 2 neutrons, 2 protons. big, heavy, slow moving. dont penetrate far into materials, stopped quickly even by air. size = strongly ionising(knock electrons off atoms and create a lot of ions)
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What is a beta particle?
electrons. quite fast, quite small. penetrate moderately, ionise moderately. for every beta particle emitted a neutron turns into a proton. no mass, charge of -1.
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What has to balance in a nuclear equation and what do they show?
show the decay of alpha and beta. the mass and atomic numbers have to balance on each side of the equation.
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What are gamma rays?
penetrate far into materials, weakly ionising as they pass through rather than collide, eventually hit something and do damage. no mass, no charge.
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What radiation is deflected by electric and magnetic fields?
beta and alpha
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What damage can radiation cause?
high dose = more risk of cancer, harms living cells, ionisation, outer of body most damaged by beta and gamma, inside body most damaged by alpha
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What is half life?
average time it takes for the number of nuclei in a radioactive isotope sample to halve
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What radiation do smoke detectors use?
weak alpha
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What radiation do tracers in medicine use?
short life beta or gamma
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What radiation does radiotherapy use?
gamma
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What radiation does sterilisation use?
gamma
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What are the precautions for radiation?
minimum exposure, no skin contact, stay far away, avoid looking directly at it, lead box/apron/screen
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What is nuclear fission?
the splitting up of a big atomic nuclei
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What is nuclear fusion?
joining of small atomic nuclei
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Other cards in this set
Card 2
Front
If there is no resultant force, how is a vehicle moving?
Back
at constant speed
Card 3
Front
If there is 0 resultant force, how is a vehicle moving?
Back
Card 4
Front
If it has a non 0 resultant force, how is the vehicle moving?
Back
Card 5
Front
When two vehicles interact what forces do the exert on eachother?
Back
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