# Shared Flashcard Set

## Details

AQA Unit 2
motion,work,electricity
32
Physics
05/19/2010

Term
 distance-time graph
Definition
 the steeper the line the greater the speedSpeed = distance / timemeasured in m/sec
Term
 velocity and acceleration
Definition
 velocity is speed in a certain direction eg 30 m/s southacceleration = change in velocity/timeAcceleration is the change in velocity per second.*A body travelling at a constant speed is accelerating if it is changes directionAcceleration measured in m/s squared
Term
 velocity-time graphs
Definition
 *slope represents acceleration so steeper the slope the greater the acceleration* if slope coming down (negative gradient) this means deceleration* area under graph is distance travelled
Term
 forces
Definition
 two objects that interact exert forces.*force is measured in Newtons*if resultant force is zero the object will carry on moving at constant speed and direction
Term
 non zero resultant force
Definition
 object will accelerate if force in same direction and decelerate if in opposite direction
Term
 force equation
Definition
 force = mass x acceleration
Term
 stopping distance
Definition
 thinking distance + braking distance
Term
 falling objects
Definition
 *weight is force due to gravity objects free fall at 10m/s squared* Weight = mass x 10*objects falling in fluid reach terminal velocity(a constant velocity)
Term
 energy and work
Definition
 work done = force x distance moved *measured in joules*work is done whenever an object moves
Term
 kinetic energy
Definition
 energy of movement *depends on mass and speedkinetic energy= 1/2 mass x speed squared
Term
 momentum
Definition
 all moving objects have momentum momentum = mass x velocitymeasured in kilogram metre/sec (kg m/s)*whenever objects interact no momentum is lost (momentum is conserved) as long as no other external forces are acting
Term
 explosion
Definition
 in an explosion (eg gun being fired) the objects move in equal and opposite directions with equal and opposite momentum*bullet moves off with equal and opposite momentum as gun recoils
Term
 changing momentum
Definition
 force = change in momentum/time taken*the more time an impact takes the less force
Term
 electrical charges
Definition
 like charges repell.Unlike charges attract*When 2 electrically insulating materials are rubbed together electrons are rubbed off 1 onto the other. which way they go depends on the material*the material that gains electrons becomes negatively charged
Term
 electric current
Definition
 *rate of flow of charge*a metal can only hold charge if it is off the ground.*it is earthed if connected to ground* the bigger the charge the higher the potential difference between object and earth.*If high enough then a spark may jump across gap.
Term
 uses and dangers of staic electricity
Definition
 uses eg electrostatic paint sprayer positively charged and item being painted negatively charged then paint spreads out when hits object.eg photocopiers -copying plate charged so when light hits it black ink powder ia attracted and leaves image.dangers eg filler pipe on road tanker are earthed so no sparks which would cause explosion
Term
 electrostatic situations
Definition
 *a spark can make powder grains expode*to eliminate static use antistatic materials and earth metal objects
Term
 electric circuit symbols
Definition
Term
 resistance
Definition
 Resistance is the opposition to charge flowingresistance= potential difference/currentmeasures in ohms*current is measured by an ammeter
Term
 resistance
Definition
 in a filament lamp resistance increases with higher temp of filamentin a diode forward resistance is low, backward resistance is highin a thermistor resistance decreases if temp increasesin light dependent resistor(LDR) reistance decreases if light increases
Term
 alternating current
Definition
 repeatedly reverses direction*mains electricity is alternatingA mains circuit has a live wire which is alternately positive (+325)then negative (-325)every cycle.*It also has a neutral wire which is zero volts
Term
 in the uk
Definition
 mains supply has frequency of 50 Hertz which means it alternates 50 times each second
Term
 cells and batteries
Definition
 current travels in 1 direction only
Term
 cables and plugs
Definition
 cables have 2 or 3 insulated copper wires surrounded by plastic flexible case.Sockets and plugs made from stiff plastic which enclose electrical connection*Live wire -BROWN*Neutral wire -BLUE*Earth wirw -YELLOW AND GREENPins made of brass as good conductor
Term
 fuses
Definition
 contains a thin wire that melts and cuts off current if too much current flowing throughfuse rating should be slightly higher than the normal working current of appliance
Term
 circuit breaker
Definition
 electromagnetic switch that opens (trips) and cuts off current if too much passes through
Term
 electric power
Definition
 power = energy transformed/timemeasured in wattsElectrical power= current x potential difference
Term
 appliances
Definition
 when electric current flows through an appliance electrical energy is transformed to other formsenergy transformed = potential difference x chargecharge = current x time
Term
 nuclear reactions
Definition
 alpha decay nucleus loses 2 protons and 2 neutrons which are emitted as an alpha particlebeta decay neutron changes to proton and an electron is created and emitted as a beta particle
Term
 rutherford
Definition
 rutherford used measurements from alpha scattering experiment to prove that an atom has a small positively charged nucleus which contains most of the mass
Term
 nuclear fission
Definition
 occurs when a neutron collides and splits a uranium -235 nucleus or a plutonium 239 nucleuschain reaction occurs when neutrons from fission go on to cause further reactions.In a nuclear reactor every fission causes 1 other fission.
Term
 Nuclear fusion
Definition
 joining of 2 atomic nuclei to form a single larger nucleus. During this process energy is released.This is the process which happens in starsNuclei approaching one another repel as they are poitively charged this is overcome by heat and contained by a magnetic field.
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