Physics Flashcards
(97 cards)
1
Q
The steeper the line on a distance time graph
A
The greater the speed
2
Q
Velocity is
A
Speed in a given direction
3
Q
Acceleration is
A
The change of velocity per second
4
Q
The equation for acceleration is
A
A= V-U/T A- acceleration V- final velocity U- initial velocity T- time
5
Q
If the line on a velocity time graph is horizontal
A
The acceleration is zero
6
Q
The area under the line on a velocity time graph is
A
The distance travelled
7
Q
A force can change the
A
Shape of an object or change its motion or state of rest
8
Q
The unit of force is
A
Newton
9
Q
When two objects interact they
A
Always exert equal and opposite forces on each other
10
Q
The resultant force is
A
A single force that had the same effect as all the forces acting on an object
11
Q
If an object is accelerating
A
There must be a resultant force acting on it
12
Q
The bigger the resultant force
A
The greater its acceleration
13
Q
The greater the mass of an object
A
The smaller it’s acceleration for a given force
14
Q
Equation for resultant force
A
F=mXa
F- resultant force
M- mass kg
A- acceleration m/s^2
15
Q
Friction and air resistance oppose
A
The driving force of a car
16
Q
The stopping distance of a car depends
A
on the thinking distance and the braking distance
17
Q
The weight of an object is
A
The force of gravity on it it’s mass is the quantity of matter
18
Q
The terminal velocity of a falling object is
A
The velocity it reaches when it is falling in a fluid the weight is then equal to the drag force on the object
19
Q
The extension is
A
The difference between the length of the spring and it’s the original length
20
Q
The extension of a spring is
A
Directly proportional to the force applied to it provided the limit of proportionality is not exceeded
21
Q
The spring constant of a spring is
A
The force per unit extension needed to stretch it
22
Q
Equation for Hookes law
A
F=kXe
F- force
K- spring constant
E- extension
23
Q
Fuel economy of road vehicles can be improved by
A
Reducing the speed or fitting a wind deflector
24
Q
Average speed cameras are
A
Linked in pairs and measure average speed
25
The gradient of the line on a distance time graph represents
An objects speed
26
A force can
Change the shape of an object or change its motion or state of rest
27
When two objects interact the always
Exert equal and opposite forces on each other
28
What is terminal velocity
Terminal velocity of a falling object is the velocity it reaches when it is falling in a fluid. The weight is then Equal to the drag force on the on the object
29
Explain work done
Work is done on an object when a force makes the object move
Energy transferred=work done
Work done to overcome friction is transferred as energy that heats the objects that rub together and the surroundings
30
Describe GPE
GPE is energy stored in a object because of its postions in Earths gravitational field. The GPE of an object depends on its weight and how far it moves vertically
31
What is kinetic energy
The kinetic energy of a moving object depends on its mass and speed
All objects have kinetic energy
The greater the mass and the faster the speed of an object the more kinetic energy it has
32
What is elastic potential energy
Elastic potential energy is the energy stored in an elastic object when work is done on the object
33
Momentum
The greater the mass and the greater the velocity of an object the greater its momentum
When objects interact the total momentum before the interaction is equal to the total momentum afterwards
34
What are explosions
When two objects are at rest their momentum is zero. In An explosions the objects move apart with equal and opposite momentum. One is positive and one is negative so the total momentum after the explosion is zero
35
What is an impact force
When a force acts on an object that is able to move its momentum changes
For a particular change in momentum the longer the time taken for the change the smaller the force that acts
In a collions the momentum of an object often becomes zero during the impact the object cames to rest
36
Describe charging by friction
Electrons have a negative charge so the material that has gained electrons becomes negatively charged. The one that has lost electrons is left with a positive charge
37
Ohms law
States that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor
Reversing the current through a component reverses the potential difference across it
38
What shape is the line on a current- potential difference graph for a filament bulb
A curve as current is not directly proportional to the potential difference
39
For components in series
The current is the same in each component
Adding the potential differences gives the total potential difference
Adding the resistances gives the total resistance
40
For components in parallel
The total current is the sum of the currents through the Somerset components
The bigger the resistance of a component the smaller the current is
41
In a parallel circuit the potential difference is
The same across each component
42
Direct current is
In one direction only
43
Alternating current
Repeatedly reverses its direction
44
The peak voltage of an alternating potential difference is
The maximum voltage measured from zero volts
45
A mains current has
A live wire that is alternatively positive and negative every cycle and neutral wire at zero volts
46
What are sockets and plugs made of
Stiff plastic materials which enclose the electrical connections
47
What do cables consist of
Two or three insulated copper wires surrounded by an outer layer of flexible plastic material
48
What is in a three pin plug
Live wire- brown
Neutral wire - blue
Earth wire- green or yellow
49
What is the earth wire used for
It is to earth the metal case of a mains appliance
50
What does a fuse contain
A thin wire that heats up and melts if too much current passes through it. This cuts off the current
51
A current breaker is
An electromagnetic switch that opens/ trips and cuts the current off if too much current passes through it
52
A residual current circuit breaker RCCB
Cuts off the current in the live wire if it is different to the current on the neutral wire. It works faster than a fuse or an ordinary circuit breaker
53
The power supplied to a device is
The energy transferred to it each second
54
An electric current is
The rate of flow of charge
55
When charge flows through a resistor
Energy transferred to the resistor makes it hot
56
Electrical faults are dangerous because
They can cause electric shocks and fires
57
A radioactive substance contains
Unstable nuclei that become stable by emitting radiation
58
There are theee main tiles of radiation form radioactive substances
Alpha, beta, and gamma radiation
59
Radioactive decay is a
Random event- we cannot predict or influence when it happens
60
Background radiation come from
Radioactive substances in the environment, or from space, or from devices such as X-ray machines
61
Rutherford used the measurement from which particles
Alpha particles, scattering experiments as evidence that an atom has a small, positively charged, central nucleus where most of the mass of the atom located
62
The nuclear model if the atom correctly explained what
Why the alpha particles are scattered and ehh some are scattered through large angles
63
What are isotopes of an element
They are atoms with the same number of protons but different numbers of neutrons. Therefore they have the same atomic numbers but different mass numbers
64
Alpha radiation is
Stopped by paper or a few centimetres of air
65
Beta radiation is stopped by
Thin metal or about a metre of air
66
A magnetic or electric field Can be used to
Separate a beam of alpha, beta, and gamma radiation
67
Alpha, beta, and gamma radiation ionise which substances
The ones they pass through
68
What is ionisation
Any process in which atoms become charged
69
Alpha particles have a
Positive charge and are deflected by electric and magnetic fields
70
Beta particles have
A negative charge and are deflected by electric and magnetic fields in the opposite direction to alpha particles
71
Gamma rays are
Electromagnetic waves so they will travel a long way through a material before colliding with an atom
72
What is half life
The half life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve
73
The activity of a radioactive source is
The number of nuclei that decay per second
74
What decreases by every half life
The number of atoms of a radioactive isotope and the activity
75
The use we can make of a radioactive isotope depends on
It's half life, and the type of radiation it gives out
76
What are alpha sources used for
Smoke alarms the are not dangerous because they see very poorly penetrating the source needs a half- life of several years
77
Beta sources are used for
Thickness monitoring in the manufacturing of things like paper or metal foil, the source needs a half-life of many years so that decreases in count rate are due to changes in the thickness of the paper
78
Gamma and beta sources are used
As tracers in medicine, the source is injected or swallowed by the patient. It's progress around the body is monitored by a decor outside the patient. The source needs a half life of a few hours so that the patient is not exposed to unnecessary radioactivity
79
For radioactive dating of a sample
We need a radioactive isotope that is present in the sample which has a half life about the same as the age of the sample
80
Nuclear fission is
The splitting of a nucleus into two approx equal fragments and the release of two or three neutrons
81
Nuclear fission occurs when a neutron hits what
A uranium-235 nucleus or a plutonium-239 nucleus and the nucleus splits
82
A chain reaction occurs when
Neutrons from the fission go on to cause other fission events
83
In a nuclear reactor control rods absorb fission neutrons to ensure that
Only one neutron per fission goes in to produce further fission
84
Nuclear fission is the process of
Forcing two nuclei together so they form a single larger nucleus
85
Energy is released when
Two light nuclei are fused together
86
Radon gas is an
Alpha emitting isotope that seeps into houses in certain areas through the ground
87
What is nuclear waste stored in
Safe and secure conditions for many years after unused uranium and plutonium is removed from it
88
A galaxy is a collection of
Billions of stars held together by their own gravity
89
Before galaxies and stars formed what was the universe formed of
Hydrogen and helium
90
A protostar is
A gas and dust cloud in space that can go on to form a star
91
Low mass star
Protostar- main sequence star- red giant- white dwarf- black dwarf
92
High mass star
Protostar- main sequence star- red supergiant- supernova- black hole if sufficient mass
93
The sun will become
A black dwarf
94
A supernova is
The explosion of a supergiant after it collapses
95
Elements as heavy as
Iron are formed inside stars as a result of nuclear fusion
96
Elements heavier than iron are formed in
Supernovas, along with lighter elements
97
The sun and the rest of the solar system were formed
From the debris of a supernova
