P2 Flashcards
(119 cards)
1
Q
What is the definition of speed?
A
how fast you’re going no regard to direction
2
Q
What is defition of velocity
A
How fast you’re going in a particular direction
3
Q
What is the equation for speed?
A
speed = distance divided by time
4
Q
define “gradient” on a distance time graph
A
Speed
5
Q
What does it mean when a line is flat on a distance/time graph?
A
Stationery, vehicle has stopped
6
Q
The steeper the line on a distance time graph the….
A
the faster the object is going
7
Q
What does it mean when the line is going downwards on a distance time graph?
A
Going back towards starting point
8
Q
What do curves represent on distance time graphs?
A
acceleration or deceleration
9
Q
What does a steep curve mean on a distance time graph?
A
Speeding up
10
Q
What does it mean when a curve is levelling off on a distance time graph?
A
Decreasing gradient
11
Q
What is speed measured in?
A
mph or m/s
12
Q
What is velocity measured in?
A
mph (NSEW) or m/s then degrees e.g. 60°
13
Q
What is acceleration?
A
How quickly velocity is changing
14
Q
Whats the equation for acceleration?
A
Change in velocity divided by time taken
15
Q
What is acceleration measured in?
A
m/s2
16
Q
EXAMPLE: If a skulking cat accelerates from 2m/s to 6m/s in 5.6s. Find its acceleration.
A
a= ( v-u) / t = (6-2) / 5.6 = 4 / 5.6 = 0.71m/s2
17
Q
What does this mean: (v-u) / a or t
A
V = final velocity and U = initial velocity / acceleration or time
18
Q
What does the gradient mean on a velocity-time graph?
A
Acceleration
19
Q
What does a flat section represent on a v-t graph?
A
Steady speed
20
Q
The steeper the graph on a v-t graph the…
A
Greater the acceleration or deceleration
21
Q
An uphill section on a v-t graph (/) is….
A
acceleration
22
Q
Downhill sections on a v-t graph () are
A
Deceleration
23
Q
What is gravitational force all about?
A
Force of attraction between all masses. Gravity attracts all masses and anything near a planet or star is attracted to it very strongly. On a surface of a planet it makes things accelerate, and it gives everything a weight.
24
Q
Define the word “mass”
A
Amount of stuff in an object
25
What is weight?
Caused by pull of gravitational force. Things would weigh different on different planets because if gravitational force.
26
Would the mass be the same on the moon as it is on earth?
Yes because all masses are the same no matter where
27
What is weight (force) measured in?
Newtons (N)
28
What is mass measured in?
Kg
29
What is the equation to work out the weight of an object?
W = m x g
30
What does this stand for (give units): w = m x g
W = weight (N) m = mass (kg) g = strength of gravity (N/kg)
31
EXAMPLE: What is the weight, in newtons of a 5kg mass both on Earth and the moon?
(w = m x g) On earth: g = 10N/kg W = 5x10=50N
| On moon: g = 1.6N/kg W = 5x1.6 = 8N
32
What is "resultant force"
Overall force on a point of object
33
What is static electricity?
When certain materials are rubbed together, electrons are transferred from one material to the other. A positive charge is left on one and a negative charge on the other, depends on the material.
34
What happens when you rub a polythene rod with a cloth duster cloth?
The electrons go from the duster to the rod so the rod has a negative static charge and the duster cloth positive.
35
What happens when you rub an acetate rod with a duster cloth?
Electrons move from the rod to the duster cloth. Duster now has a negative static charge, rod has a positive static charge.
36
What happens to electrons in static electricity?
Only electrons move. A positive static charge is always caused by electrons moving away elsewhere.
37
Why are some things good conductors?
Electrical charges move easily through some material (conductors). metals are good conductors
38
explain "current" in an electrical circuit
Flow of electric charge round the circuit. It will only flow if there is a potential difference. Measured in ampere/amps/A
39
What is potential difference?
Driving force that pushes current around. SAME as voltage. measured in volts/V
40
What is resistance in an electrical circuit?
Anything in the circuit which slows flow (current) down. measured in Ohms, Ω
41
What happens if resistance is greater?
Greater the resistance across a component, the smaller the current that flows
42
What does Q = I x t mean?
Charge (coulombs C) = current (A) x time (s)
43
A battery charger passes a current of 2.5A through a cell over a period of 4 hours. How much charge does the charger transfer to the cell altogether?
Q = I x t. 2.5 x (4x60x60) = 36 000 C.
44
What does W = V x Q mean?
work done (J) = potentional difference (V) x charge (coulombs)
45
What does an ammeter do in a circuit?
Measures the current in amps, must be place in main circuit not parallel circuit
46
What does a voltmeter do in a circuit?
measures potential difference (voltage in volts). Must be placed parallel to a component but NEVER parallel to resistor
47
Whats a very basic circuit used for?
Testing components to then make a V-I graph
48
What three things can be put randomly in a series circuit?
Component, ammeter, variable resistor
49
What does the variable resistor do?
Alters current flowing through a circuit so several readings can be taken from ammeter and volt meter to get V-I graph. and find resistance
50
What happens to resistance when temperature increases?
Increases
51
explain why resistance increases with temperature?
heat energy causes ions in the conductor to vibrate more, with ions vibrating it's more difficult for charge-carrying electrons to get through resistor, the current can't flow so resistance increases.
52
What is V=IR
Potential difference (V) = current (A) x resistance (Ω)
53
Voltmeter V reads 6 V and resistor R is 4Ω. What is the current through Ammeter A?
I =V/R. 6/4 = 1.5 A.
54
Explain a diode.
Made from a semiconductor such as silicon. Used to regulate the voltage in circuits. Lets current flow freely in ONE direction but not the other due to a high resistance
55
What do light emitting diodes do?
LED, emits light when a current flows through it in the forward direction. Used in smaller circuits, traffic lights, remote controls, digital clocks
56
What does an LDR do?
resistor that is dependant on intensity of light. IN bright light, resistance falls, in dark light resistance is at its highest.
57
What happens to thermistor as temperature increases?
resistances decreases. Thermistor is a temperature dependant resistor. In hot conditions, resistance drops. In cold weather, the resistance goes up
58
Whats involved in a series circuit?
Potential difference is SHARED. current is the SAME everywhere. Resistance adds up to make a total. Cell voltages add up to make a total.
59
Whats involved in a parallel circuit?
Potential difference is the SAME across all components. current is SHARED.
60
Whats the mains supply for the UK?
230 V.
61
How do you work out the voltage in a series circuit?
half the resistance.
62
Everything electrical in a car is...
a parallel circuit
63
Whats is the mains supply?
Its an alternating current so current is constantly changing direction. The frequency of the mains supply is 50 Hz.
64
What type of current do batteries and cells produce?
Direct current, current flows in same direction.
65
What is an oscilloscope?
CRO, a voltmeter. If you plug in an AC supply, you get a trace that shows how high the voltage of the supply changes with time - Regular pattern. If you plug in DC supply, straight line. The vertical height of AC shows input voltage at that point. For DC voltage is just the distance from straight line trace to the centre line.
66
What are the nine main hazards in a home?
long cables, frayed cables, cables in contact with something wet or hot. Water near sockets, shoving things in socket. damaged plugs, too many plugs in one socket, lighting sockets without bulbs in. appliances without their covers on.
67
what are the three wires in a cable?
Earth, live, neutral
68
Describe the earth wire
green and yellow, earth wire, for safety prevents fire and shocks when fuse breaks. carries electricity to earth and away from you to prevent damage
69
Describe the live wire
Brown, live wire, alternating current between positive and negative voltage
70
Describe the neutral wire
always at OV, blue, electricity flows in and out through live and neutral wires only
71
whats featured in the wiring of a plug?
right coloured wire connected to each pin, firmly screwed in. no bare wires showing, cable grip tightly fastened over cable outer layer. different appliances need different amounts of electrical energy
72
what do thicker cables have?
less resistance, carry more current
73
state some features of a plug
metal parts are made of copper or brass because they're good conductors. The case, cable grip and cable insulation are made of rubber and plastic because good insulators
74
What happens when you press the brakes (car)?
reduce kinetic energy of car by transferring it into heat and sound
75
How do electric or hybrid cars use KE energy usefully when braking?
regenerative brakes use the system that drives the vehicle to do majority of breaking. brakes put motor in reverse, wheels are slowed. motor acts as electrical generator converting KE into electric which is stored as chemical
76
describe how a fuse may break
If a live wire happens to touch the metal casing, big surge of current out through earth wire, surge in current melts the fuse, when current is greater than fuse rating - cuts off live supply. no electric shock
77
What does it mean by double insulated?
Metal cases are usually earthed. earth wire cased by plastic, NO metal parts showing.
78
What are some ads and disads of circuit breakers?
bit like fuses but better. when a surge in current is detected, they break circuit by opening a switch. can be easily reset by flicking a switch on device - more convenient. more expensive than fuses
79
What do all resistors produce when current flows through them?
heat - more current more heat
80
E = p x t
energy transferred (J) = power rating (W) x time (s)
81
power = current x potential difference what are the measurements
power = watts, current = amps, potential difference = volts
82
What did Rutherford discover?
Plum pudding model. Fired a beam of alpha particles at thin gold foil, expected positively charged alpha particles to be slightly deflected by electrons but most went straight through. came up with nuclear model of atom
83
Where can background radiation come from?
manmade - buildings, food, X-rays, nuclear plant
| non manmade - rocks, cosmic rays (sun), rocks
84
How are cars designed to convert KE safely in a crash?
Crumple zones, side impact bars, seat belts, air bags
85
What is a crumple zone?
at the front and back of car. crumple on impact, increase impact time decreasing force produced by change in momentum
86
What is a side impact bar?
strong metal tubes fitted into car door panels. They help direct KE of crash AWAY from passengers to other areas.
87
How does a seatbelt reduce KE in crash?
increasing time for wearer to stop. reduces force acting in chest, some KE is absorbed by seatbelt by stretching
88
What do airbags do to protect you?
slow you down more gradually, stop you hitting hard surfaces
89
what does aerodynamic mean?
car is shaped in a way that air flows easily and smoothly past them - decreases air resistance.
90
How do cars reach their top speed?
when resistive force equals driving force provided by engine, with less air resistance to overcome, car can reach a higher speed, aerodynamic cars have higher top speeds
91
What factors affect total stopping distance/
the sum thinking and braking distance
92
How does thinking distance affect stopping distance?
the faster you're going, the further you'll go. How aware you are - drugs, tiredness, alcohol, not concentrating
93
What is braking distance?
the faster you're going the longer it takes to stop. How good your brakes or tyres are. How good the grip is, e.g. weather, road surfaces, tyres.
94
What happens when a force moves an object through a distance?
energy is transferred and work is done
95
what's the formula for work done?
work done (J) = force (N) x distance (m)
96
What's the formula to work out GPE?
GPE (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
97
What is the gravitational field strength on earth?
10 N/kg
98
KE equation is
kinetic energy (J) = 1/2 mass x speed2
99
how does KE depend on mass and speed?
the more an object weighs, and the faster its going, the bigger the kinetic energy will be
100
How do you work out KE when a car is stopping?
1/2mv2 = F x d
101
what does 1/2mv2 = F x d mean?
kinetic energy transferred (kgm/s) = braking force (N) x braking distance (m)
102
when kinetic energy is gained....
potential energy is lost
103
What happens when a meteor enters the atmosphere?
very high KE. Friction due to collisions with particles in atmosphere transfer some of their KE to heat energy, work is done. temp. can become so extreme most meters burn up and never reach earth
104
What is F = k x e
Force (N) = spring constant (N/m) x extension (m)
105
an elastic object is.....
directly proportional to force
106
What happens when you stretch an elastic object too far?
it has a limit of proportionally and maximum force the object can withstand. it will become permanently stretched so will be longer than before
107
How do you work out power of something?
power (Watts) = work done (J) / time taken (s)
108
Explain momentum
property of moving objects. greater mass of object, greater the velocity, more momentum
109
What is p = m x v
momentum (kgm/s) = mass (kg) x velocty (m/s)
110
what does it mean by closed system
no external forces act
111
What type of radiation do smoke detectors use?
alpha radiation α
112
How is gamma and beta used as tracers in medicine?
iodine-131 is absorbed in thyroid gland like normal iodine-127, but it gives out radiation which can be detected to see whether the gland is taking in iodine as it should. have to be gamma or beta so radiation can pass out body
113
How is gamma radiation using to treat cancer?
gamma can kill all living cells so radiotherapy is used to kill cancer cells. has to be done carefully, and correct amount of dosage. it will kill normal cells making patient very ill
114
Why is food exposed to a high dose of gamma rays?
kills all microbes keeping the food fresh for longer. food is not radio active afterwards though.
115
whats the most dangerous radiation OUTSIDE the body?
beta and gamma
116
What is most radiation dangerous inside the body?
alpha because it can damage a localised area
117
name some safety precautions for when handling radioactive sources
never allow source to touch skin, only use for a short time, hold source at arms length. don't look directly at source, always store radioactive sources in LEAD containers.
118
What is nuclear fission?
splitting up of big atomic nuclei. slow moving neutron absorbed by uranium 235 or plutonium 239, nucleus becomes unstable so it splits, spits out two or three neutrons which may be absorbed again causing a chain reaction
119
what is nuclear fusion?
joining of small atomic nuclei. can only happen at extremely high temperatures and extremely strong magnetic field. produces lots of energy and hydrogen but barely any radioactive waste
