P2 Flashcards
1
Q
What is the primary measurement for speed and velocity?
A
M/S
2
Q
What is the difference between speed and velocity?
A
speed is how fast. you are going, velocity takes into account the direction you are going eg 30 m/s north
3
Q
how do you calcualte the speed
A
speed = distance over time
4
Q
what does the gradient of a distance time graph tell you?
A
How fast your object is going
5
Q
how do you find the speed in a dt graph,
A
gradient
6
Q
What is a flat section in a dt graph
A
the object. is stationary
7
Q
what do straight uphill or downhill slopes mean on a dt graph
A
the object. is travelling at a steady speed
8
Q
what do downhill lines mean in a dt graph
A
that the object is going back to its starting point
9
Q
what does a steeper graph mean
A
the object if going faster
10
Q
what do curves mean in a dt graph
A
acceleration or decceleration
11
Q
wht is acceleration
A
how quickly the velocity is changing
12
Q
how do you find the acceleration
A
change in velocity over time taken
13
Q
what is the gradient in a vt graph
A
acceleration
14
Q
what is a flat section in a vt graph
A
steady soeed
15
Q
what is a uphill/downhill slope in a vt graph
A
acceleratikn/deceleration
16
Q
what does gravitational force do
A
it makes all things accelerate towards the ground, all with the same acceleration which is about 10 m/s squared on earth
17
Q
What is the difference between weight and mass
A
Mass is the ammount if stuff inside an object it is the same anywhere in the universe. weight caused by the pull of the gravitational force
18
Q
how do you measure mass
A
kg
19
Q
how do you measure weight
A
N
20
Q
how do you find the weight
A
mass X gravitational feild streingth
21
Q
what is the resultant force
A
if you have a number of forces acting upon a single point, you can replace then with a single force, as lomg as it has the same effect on the motion as the original forces acting all together, of the forces all act upon the same line (theyre all paralel and act in the same opposite direction) the overall effect is found by just adding or subtracting them, the overall force you get is called the resultant force
22
Q
what dies an object need to start moving
A
a force
23
Q
what happens if there is no resultant force on a moving object
A
there will be no change in velocity and so it will keep moving
24
Q
what happens if there is a non zero resultant force applied on an object
A
the object will accelerate in the direction of the force
25
what is the formula for a resultant force producing acceleration
F = ma
f is the resultant force in newtons
m is the mass in kilograms
a is the acceleration in meters per second squared
26
what happens when 2 object interact
the forces they exert on each other are equal and opposite
27
why will an object that has ni force propelling it always stop
because of friction
28
what directiom does friction always act
opposite to movement
29
how is most of the resistive force caused?
by drag
30
what is the most important factor in reducing drag in fluids
keeping the shape of the object streamlined
31
what causes frictional forces in fluids to increase
speed
32
wht do falling object accelerate when they first set off
because the force of gravity is much more than the force of frictikn slowing them down, so they accelerate, as the speed increases the friction builds up, this gradually reduces the acceleration until eventually the frictional force is equal to the accelerating force and the. it wont accelerate any more, this is the terminal velocity and it will now fall at a steady speed
33
what is the accelerating force acting upon all falljng objects and why do some fall at different rates
it is gravity and they fall at different rates due to air resistanc
34
how it the terminal velocity of an object determined?
its drag in comparison to its weight
35
what does the frictional force of an object depend on
its shape and area
36
what is the stopping distance
the distance from an objest to start to stop to it comming to a complete stop
37
what is thinking distance effected by
how fast you are going
| how 'sharp' you are
38
what is braking distance effected by
how fast your going
how good your breaks are
how good the tyres are
how good the grip is
39
expain how work is done
whenever something moves, some thing else is transferring energy into it, this means that the thing transferring energy needs an energy supply, it then dkes work by moving the object amd one way or another it transferres the energy it receives as fuel as other forms
40
explain wasted energy
when energy is transferred from one thing to another, some of it is transfered as useful energy but some of it can be wasted eg heat from a tv
41
what is the formula for work done?
work done = force X distance
42
how do you find gravitational potential energy and what does g stand for
mass X g X height
g is for the gravitational feild strength, on earth it it 10N/kg
43
what is the formula for kinetic energy
1/2 x mass x speed squared
44
show kinetic energy transferred = work done by brakes and what all the letters mean
1/2 x m x v squared = f x d
1/2 x mass x speed squared = maximum breaking force x breaking distance
45
what is the same as kinetic energy gained
= potential energy lost
46
what is elestic potential energy
object that can mkve back to their original shape are elastic objects, when an elestic object is moved out of shape, the energy is stored from the work done to it as epe (just ez to type) and when released the energy will be turned to kinetic energy and it will move back to shape
47
what is the limit of proportionality in term of elastic objects
the maximum force that the elastic object can take and still extend proportionally
48
what is the formula for power
power = work done or energy transferred over time taken
or p= e over t
49
what is the proper unit of power
a watt, it is one joule of energy transferred per second
50
what js a watt the same as
a joule per second
51
explain a way in which you could calculate your power output
find out how long it takes you to accelerate from 0 m/s to a specific soeed eg 8 and then apply it to this formula energy transferred over time
52
how do you find momentum
mass x velocity
53
explain cinservation of momentum
in a closed system, the total momentum before an event eg a collision equals the total momentum after the event
54
how do forces caise changes im momentum
when a force acts upon an object, it causes a change im momentum. A larger force means a faster charge of momentum (and so a greater acceleration)
55
How are cars designed to convert kinetic energy safely in a crash
if a car crashes, it will slow down very quickly, this means that a lot of kinetic energy is converted into other forms of energy in a short amount of time which cna be dangerous for people inside. In a crash, there will be a big change in momentum over a very short time so the people inside experiance huge forces that can be fatal
cars are designed to convert the kinetic energy by increasing the time over which momentum changes happens, which lessens the forces on the passengers
56
name some ways cars are designed to convert energy safely in a crash
crumple zones at the front and back of the car crumple up on impact, the cars kinetic energy is converted into other forms of energy by the car body as it changes shape. Crumple zones increase the impact time, decreasing the force produced by change in momentum.
side impact bars are strong metal tubes fitted into car door panels. They help direct the kinetic energy of the crash away from the passengersto other areas of the car, such as crumple zones
seat belts streatch slightly, increasing the time taken for the wearer to stop. This reduces the forces acting in the chest. Some of the kinetic energy of the wearer is absorbed by the seat belt stretching air bags also slow you down more gradually from hitting hard surfaces inside the car
57
how do cars reach top speed
when their resistive forces equals the driving force provided by the engine
58
what is the typical power output for a small car and a sports car
50 kW for a small car
| 100 kW for a sports car
59
what is build up of staric caused by
friction
60
explain how build up of static is caused by friction
when certain insulating metals are rubbed together, negatively charged electrons will be scraped off one and dumped in the other, this will leave a positive static on one and a negative static on another,
61
can charges move and can electrons move
electrons can charges cant
62
why do opposite chatprges attract
because they exert a force on one another
63
can charges move through conductors
yes
64
what is current
the flow of electric charge round the circuit. Current will only flow through a component kf there is a potential difference across that component the unit for current is amperes or amps or a
65
what is potential difference in a circuit
the driving force that pushes the current round, unit, volt v
66
what is resistance in a circuit
anything in a circuit that slows the flow down unit ohm
67
what is the relationship between resistance and current in a component
the greater the resistance, the smaller the current
68
what does the total charge through a circuit deoend on?
current and time
69
what is the formula for current
current = charge over time
i = q over t
70
what is the formula for potential difference
work done over charge
w over q
71
what is an ammeter
something that measures the current in amps flowing through the component, it must be placed in series, it can be put anywhere in the series but never in parallel
72
what is the voltmeterr
it measures the potential difference in volts across the component
it must be placed in paralles around the component under test, not around the variable resistor or the battery
73
what happens if you vary the variable resistor
it alters the current flowing through the circuit
74
what does resistance increase with and how
temperature because as an electrical charge flows through a resistor, some of it becomes hot, this vibrates the particles to it is harder for them to get through so the resistance increases
75
what is the formula for potensital difference
current x resistance
76
what is a diode
a diode is a special device made from semiconductor material such as siliconl, its used to regulate the potential difference in circuits. It lets current flow freely through it in one direction, but not in the other ie theres a very high resistance in the other
77
What are light emmitting diodes
a light emmiting diode (LED) emmits a light when current flows through it in the forwards direction, they are being used more and more as lighting, as they use a much smaller current than other forms of lighting, they indicate the presence kf current in a circuit
78
What is a light dependant resistor (LDR)
A resistor that is dependant on the intensity of the light, in bright light the resistance falls, in darkness the resistance is highest, they are used in burglar alarms and automatic night lights
79
What is a thermistor
a thermistor is a temperature dependant resistor, in hot conditions the resistance drops, in cool conditions, the resistance goes up. Thermistors make useful temperature detectors eg car engine temperature sensors
80
what are series circuits
in series circuits the different components are connected in a line end to endbetween the positive and negative end of the power supply except for voltmeters, which are connected in parallelbut they dont count as part of the circuit, of one thing disconnects the whole circuit shuts down
81
what happens to the pd in a series circuit
it is shared between the various components. so all the voltages round a series circuit always add up to equal the source voltage
82
is current the same everywhere in a series circuit
yes, the size of the current is determined by the total PD of the cells and the total resistanceof the circuit
83
how do you find the total resistance in a series circuit
add up all the resistances in the components of the circuit, the bigger the resistance of a component, the bigger the share of the total PD
84
How do you find the cell voltage total
add up all the seperate cell voltages
85
what are parallel circuits
they are circuits in which each component is seperately connected to the positive and negative end of the supply, if you remove one of them it will hardly affect the others at all
86
is the pd seperate or all the same in each component in a series cell
all the same in each component
87
what happens to current in a parrelel circuit
it is shared between each branch, in parallel circuits the total current flowing around the circuit is equal to the total of all the currents through the seperate components
88
what are the exceptions to the parralel and series circuit rules
voltmeters and ammeters,
ammeters are always connected to the series even in a parallel circuit
voltmeters are always connected in parallel with a component even in a series circuit
89
what do potential differences add up to equal?
the osurce pd
90
what is the total resistance
the sum of the resistances in a circuit
91
give an example of something used in a series circuit
christmas lights
92
why is a parallel circuit needed in a car
so that everything can be turned off and on seperately and so everything always gets the full voltage of the battery
93
what is the ac and dc stand for in mains and batters supply
alternaiting current and direct current
94
what is a cathode ray oscilloscope
if you plug an ac supply into an oscilloscope, you get a trace on the screen that goes up and down to show how the voltage supply changes in time in a regular pattern.
95
what does the vertocal height on a oscilloscope mean
it shows the input voltage
96
what is the firmula to find frequency
frequency (Hz) = 1 over the time period
97
what are the 3 wires in a cable and what are they for
the livewire (brown) alternates between a positive and negative voltage
the neutral wire (blue) is always at OV electricity normally flows in and out through
the earth wire (yellow and green) is for protecting the wiring, and for safety, it workd together with a fuse to prevent fire ans shocks
98
what are the metal parts of the inside of a plug made of and why
copper or brass as they are very good conductors
99
why is the cable grip made of plastic or rubber
as they are flexible and good insulators
100
how do earthing and fuses prevent electrical overloads
if a fault develops in which the live wire somehow touches the metal case, then because the case is earthed. too great a current flows through the live wire. through the case and down the earth wire, the surge in current melts the fuse and when the ammount of current is greater than the fuse rating, this cuts off the live supply and breaks the circuit making it impossible to get an electric shock
101
why are circuit breakers better than fuses
when circuit breakers detect a surge in current in a circuit, they break the circuit by opening a switch. and they can be easily reset
102
what is a wasted product of a filament bulb
heat, because it is a heated strop of wire that is heated up so much till it glows, this means that it wastes alot of energy
103
how can we waste less heat in light bulbs
we can buy the bulbs that are more energy efficient and so less energy is wasted in heat although these are more expensive
104
why are fuses still used as aopse to circuit breakers
they are cheaper
105
how do you find the energy transferred
power x time
106
what is the formuka for power?
power = current x potential difference
107
what is the potential difference
the energy transferred per charge passed
108
what is the formuls for energy transformed
charge x potential difference
109
Who was earnest rutherford
He was the persone who descovered the nuclear mudel of the atom
110
What wa the plum pudding theory
JJ Thompson suggested that atoms were spheres of positive charge with tiny negative electrons stuck in them like plums in plum pudding
111
what is the atomic number of an element
the total number of protons in one atom of it,
112
what is the mass number of an element
the total number of protons and nuutrons in one atom of it
113
What are unstable isotopes
they are radioactive, meaning that they decay into other other elements and give out radiation.
114
Where does all radiation come from
unstable reaioactive isotopes undergoing nuclear decay and spitting out high energy particles
115
What are alpha particles
they are helium nuclei, they are relatively big and heavy and move slowly, they dint penetrate materials and can be stipped quickly
116
What are beta particles
electrons, these are in between alpha and gamma in terms of their properties. They move wuite fast and they are quite small. They penetrate moderately before colliding and are moderately ionising too. For every beta particle emmitted a neutron turns to a proton in the nucleus
117
What are gamma rays?
Gamma rays penetrate a long way into materials without being stopped, this means that they are weakly ionising because they tend to pass through rather than colliding with atoms. Eventually they hit something and do damage
118
What is radiation from space known as
cosmic rays
119
what are the relative proportions of nackround radiation
```
51% radon gas
10% cosmic rays
14% building materials and rocks
12% food
12% medical xrays
1% nuclear industry
```
120
why do pilots have a higher chance of getting some forms of cancer
because they fly at high altitudes so are more exposed to cosmic rays
121
why might underground mines be exposed to radiation more
because of all the rocks around
122
How does the nuclear chain reaction work
If a slow moving neutron gets absorbed by a uranium or plutonium nucleus, the nucleus can split. Each time a uranium or plutonium nucleus splits up, it spits out two or three neutrons, one of which might hit a another nucleus, causing it to split and keel the chain reaction going. When a large atom splits in 2 it will form 2 lighter elements. These new nuclei are usuailly radioactive because they have the wrong number of nuclei in them
