Physics Unit 2

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  • Created by: Lottie_C
  • Created on: 05-04-16 13:37
Friction
wastes energy by transferring to heat, provides grip, slippy surface has less friction, resistive force
1 of 71
resultant force
if in direction of motion causes acceleration, if against direction causes deceleration, if acting on stationary body it will accelerate in direction of resultant force
2 of 71
velocity
speed of body in given direction
3 of 71
stretching force
spring stops stretching when weight equals tension, if mass added stretches more
4 of 71
drag forces
air/water resistance, act against motion, caused by air/water particles hitting object as it moves past, increases if object moves faster/has bigger surface area
5 of 71
elastic potential energy
if apply force to elastic object it may stretch, if force removed goes back to original shape
6 of 71
thinking time reaction
time taken between spotting hazard and pressing brakes
7 of 71
thinking distance
distance travelled in reaction time
8 of 71
stopping distance
total distance travelled from spotting hazard to stopping
9 of 71
braking time
time taken to stop vehicle after brakes pressed
10 of 71
stretching a spring
spring may overstretch if too heavy force, doesn't go back to original shape, past limit of proportionality
11 of 71
mass
measure of amount of matter a body contains, kg
12 of 71
weight
force of gravity acting on mass, newtons
13 of 71
conservation of momentum
in any collision momentum is conserved, total momentum before is same as total after, provided no external forces act
14 of 71
extension
stretched length - original length
15 of 71
work done
energy can be transferred by doing work, work done when force causes body to move through distance
16 of 71
rebound
2 objects that bounce off one another
17 of 71
explosion
2 objects not moving push apart and move in opposite directions
18 of 71
coalesce
2 objects join together
19 of 71
factors affecting stopping distance
drunk, drugs, distraction, speed, mass of car, ice, worn tyres
20 of 71
distance time graphs
speed = gradient, gradient is vertical/horizontal
21 of 71
velocity time graph
acceleration is vertical/horizontal, distance is area under graph
22 of 71
regenerative braking
makes use of energy produced, stores energy in battery rather than wasting it
23 of 71
crumple zones
crumple up on impact, increase the impact time, decreasing the force produced by the change in momentum
24 of 71
side impact bars
strong metal tubes in car doors, direct kinetic energy away from passengers
25 of 71
seat belts
stretch slightly, reduces forces acting on chest, some kinetic energy absorbed by seat belt stretching
26 of 71
air bags
slow you down more gradually, prevent you from hitting hard surfaces
27 of 71
charge
given to insulating molecule by rubbing them
28 of 71
rules of electrostatics
opposite charges attract, like charges repel, charged objects attract neutral objects
29 of 71
earthing and discharge
object will charge up providing its not connected to earth by conductor
30 of 71
earth connection
when you connect an object to ground with conductor
31 of 71
What will happen if a person is the earth connection?
They will get an electric shock
32 of 71
What will happen if the dome is highly charged?
Large PD between dome and earth so it pushes electrons through the air as sparks
33 of 71
Discharging a positive object
extra electrons pulled up from earth to neutralise charge
34 of 71
insulating electrons
bound to atoms so charge cannot flow to Earth
35 of 71
gold leaf electroscope
if positive rod, electrons move up to cap, gold leaf left positive so repel and gold leaf sticks out. if negative rod used electrons pushed down stem, gold leaf repels and sticks out
36 of 71
van de graaf generator
frictions rub electrons onto belt, electrons carried up, electrons rubbed off onto dome, dome becomes negatively charged
37 of 71
perspex
friction transfers off perspex onto cloth making perspex positive
38 of 71
polyethene
friction transfers electrons on to polyethene from cloth making polyethene negative
39 of 71
PD/voltage
gives charges energy which makes them produce more velocity
40 of 71
restricting current
resistors introduce certain amounts of resistance to restrict current and protect them
41 of 71
why is resistance is opposition?
more resistance reduces current, all components have resistance
42 of 71
Diode
a component that will only conduct in one direction, used to prevent reverse currents
43 of 71
Thermistor
as temperature is higher, resistance is lower, use for thermostat
44 of 71
LED's (light emitting diodes)
conducts electricity to light up when forward biased, last longer and are cheaper, use less energy, TV standby, car lights
45 of 71
LDR's
as light intensity is higher, resistance is lower, use for street light which switch on automatically when its dark
46 of 71
Variable resistors
as current decreases bulb gets dimmer, use for dimmer switch/ volume control
47 of 71
series circuit
all components on single loop, current same through every component, PD shared, components with bigger resistance have a bigger share of PD
48 of 71
Parallel circuit
more than 1 circuit loop, PD same for every component, current splits between loops
49 of 71
choosing correct fuses
find normal current needed, choose fuse with next highest current rating
50 of 71
problems with fuses
need to be replaced, slow to respond
51 of 71
advantages of RCCB's over fuses
quick to respond, safer as they switch off quicker, reusable
52 of 71
why should RCCB's switch off if input and output different?
current thats not returning could be going somewhere else e.g. electronic shock
53 of 71
RCCB's
residual current circuit breaker, trips if current changes (current input is different to output current), respond quickly, easily switched back on
54 of 71
DC
direct current, batteries, current which flows in 1 direction only
55 of 71
AC
alternating current, mains electricity, constantly changing direction, 50Hz used for UK Mains
56 of 71
Safe wiring
all bare wires must be screwed in place, no wires 'whiskers' visible, live wires must be connected to fuse
57 of 71
3 pin plug
1 is earth pin, safety feature, 0V unless fault, yellow/green. 2 is neutral pin, PD around 0, blue. 3 is live pin, high alternating current, PD 230V, red.
58 of 71
Triple core wires
3 copper wires (conductors), made of thin copper threads, outside covered with plastic
59 of 71
isotopes
different form of same element, same number of protons, different number of neutrons
60 of 71
ionisation
atoms can gain/lose electrons to form ion. Alpha, Beta, Gamma are types of ionising radiation
61 of 71
risks of radiation
the higher the radiation dose, the more at risk you are
62 of 71
Alpha
2 neutrons and 2 protons (helium), mass of 4, charge of +2, least penetrating, strongly ionising, blocked by paper
63 of 71
Beta
moderately penetrating/ionising, charge of -1, nearly no mass, an electron, blocked by aluminium
64 of 71
Gamma
rays, type of EM wave, very penetrating, weakly ionising, no mass/charge, blocked by lead
65 of 71
Radioactive safety
outside body beta and gamma most dangerous, inside body alpha most dangerous
66 of 71
Rutherford
one or two atoms bounce back from nucleus
67 of 71
Half life
the radioactivity of a sample decreases over time, half life is the average time for number of nuclei in sample to half, varies
68 of 71
Nuclear fission
splitting up big atomic nuclei, neutron hits nucleus so its unstable, then releases 2/3 neutrons and energy
69 of 71
background radiation
comes from all around us. For example air, food, rocks, cosmic rays, human activity (hospitals), radon gas
70 of 71
radioactivity
random process, unstable nuclei are radioactive so will decay giving out alpha, beta or gamma
71 of 71

Other cards in this set

Card 2

Front

resultant force

Back

if in direction of motion causes acceleration, if against direction causes deceleration, if acting on stationary body it will accelerate in direction of resultant force

Card 3

Front

velocity

Back

Preview of the front of card 3

Card 4

Front

stretching force

Back

Preview of the front of card 4

Card 5

Front

drag forces

Back

Preview of the front of card 5
View more cards

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