things to memorise Flashcards
(126 cards)
1
Q
Estimate the mass of a person
A
70kg
2
Q
Estimate the height of a person
A
150cm
3
Q
Estimate the walking speed of a person
A
1 m/s
4
Q
Estimate the speed of a car on the motorway
A
30 m/s
5
Q
Estimate the volume of a can of a drink
A
300 cm^3
6
Q
Estimate the density of water
A
1000 kg/m^3
7
Q
Estimate the current in a domestic appliance
A
13A
8
Q
Estimate the e.m.f. of a car battery
A
12V
9
Q
Estimate the hearing range (frequency)
A
20Hz to 20000 Hz
10
Q
Estimate the young modulus of a material
A
something x 10^11
11
Q
Distance
A
Total length moved (no direction)
12
Q
Displacement
A
Distance in a certain direction
13
Q
Speed
A
Distance over time taken
14
Q
Velocity
A
Displacement over time taken
15
Q
SUVAT Equations?
A
v=u + at v^2= u^2 + 2as s=ut + 1/2at^2 s=vt - 1/2at^2 s = 1/2(v + u) x t
16
Q
Acceleration of free fall
A
9.81 m/s^-2
17
Q
Projectile motion
A
uniform velocity in one direction and constant acceleration in perpendicular direction
18
Q
Newton’s first law
A
An object remains stationary or in uniform motion unless a resultant force acts upon it.
19
Q
Newton’s second law
A
The rate of change of momentum is proportional to the resultant force and occurs in the direction of force.
20
Q
Newton’s third law
A
Every force has an equal force that occurs in the opposite reaction forming an action - reaction pair
21
Q
Mass
A
Measure of the amount of matter in the body
22
Q
Weight
A
Force of gravitational attraction on a body
23
Q
Momentum
A
mass x velocity
24
Q
Force
A
m x a; change in momentum/time taken for change
25
Principal of conservation of momentum
When bodies in a system interact, total momentum remains constant provided no external force acts on the system.
26
Perfectly elastic collision
A collision in which the total momentum is conserved. A collision in which the total kinetic energy is conserved.
27
Two identical spheres collide elastically. Initially, X is moving with speed v and Y is stationary. What happens after the collision?
X stops and Y moves with the speed of V : relative velocity before collision = - (relative velocity after collision)
28
Perfectly inelastic collision
Total energy is conserved but Ek is converted into other forms of energy. Only momentum is conserved and the particles stick together after collision.
29
Force
rate of change of momentum
30
Density
Mass per unit of volume
31
Pressure
Force per unit area
32
Upthrust
An upward force exerted by a fluid on a floating or submerged object. Caused by the difference in pressure on the bottom surface and the top surface.
33
Frictional force
Force caused by the rubbing of two surfaces
- always opposes relative or attempted motion
- always acts along the surface
34
Viscous force
Force caused by motion of an object in a fluid
- only exists when there is motion
- magnitude increases with speed of the object
35
Centre of Gravity
Theoretical point through which all the weight of an object is assumed to act.
36
Couple
A pair of forces the same size that produce rotation
- same magnitude
- same distance from pivot
- opposite direction
37
Moment
Moment = force x distance from pivot (perp.)
38
Torque of a couple
Force x distance between forces
39
Conditions of equilibrium
Resultant force equals zero. Resultant rotational force (torque) is equal to zero.
40
Principle of moments
For a body to be in equilibrium, the sum of all clockwise moments must equal the sum of all anticlockwise moments about the same pivot.
41
Pressure in fluids
Volume of water = A x h
Mass of Water = density x volume = p x A x h
Weight of water = density x volume x gravitational force = p x A x h x g
Pressure = force/area = p x A x h x g/ A = p x g x h
Therefore pressure = pgh
42
Law of conservation of energy
The total energy of an isolated system cannot change - it is conserved over time. Energy cannot be made or lost just converted between different forms.
43
Work done by a force
W = F x s
44
Work done by an expanding gas
W = pressure x change in volume
| Temperature of gas has to be constant.
45
Gravitational potential energy
W = m g h
46
Power
V x I; Work done / time taken
47
Efficiency
Useful energy output/total energy output x 100
48
Hooke's Law
The extension produced by a spring is proportional to the applied force as long as the elastic limit is not exceeded: F = k x x
49
Parallel springs
ke = k1 + k2
50
Springs in series
1/ke = 1/k1 + 1/k2
51
Stress
Stress = Force / Cross-sectional area ( Pa)
52
Strain
Extension / original length ( no units )
53
Young Modulus
ration of stress to strain; units in Pa or N/m^2
54
Elastic deformation
When deforming forces removed, the subject returns to original form
55
Plastic deformation
When deforming forces removed, the subject returns to a stretched form
56
Strain energy
The potential energy stored by an object when it is deformed elastically W=1/2kx^2
57
Displacement (wave)
Distance of a point from its undisturbed position
58
Amplitude
The maximum displacement of a wave
59
Period
The time taken for 1 complete oscillation to occur
60
Frequency
Number of oscillations past a point per unit time
61
Wavelength
Distance from any point on the wave to the next exactly similar point
62
Wave speed
Speed at which the waveform travels in the direction of the propagation of the wave
63
Progressive waves
Transfer energy from one position to antoerh
64
Wave equation
v = lambda/ time and time= 1/f therefore v = lamba x frequency
65
Phase difference
Phase difference between two waves is the difference in terms of fraction of a cycle or in terms of angles.
66
Intensity
Power / Area; intensity is proportional to amplitude squared
67
Transverse waves
Waves in which the oscillations occur at 90 degrees to the direction of propagation.
68
Longitudinal waves
Waves in which the oscillations of the wave are parallel to the direction of propagation
69
Doppler effect
Observed freqeuncy = Frequency of source ( velocity of source wave / velocitiy of source wave (+-) velocity of source)
70
Electromagnetic waves
All travel at the speed of light : 3 x 10^8
Travel in free space ( no medium )
Can transfer energy
Transverse waves
71
What is the frequency of radio waves?
10^3
72
What is the frequency of microwaves?
10^-2
73
What is the frequency of infrared
10^-5
74
What is the frequency of visible light
0.5x10^-6
75
What is the frequency of ultraviolet waves?
10^-8
76
What is the frequency of X-ray?
10^-10
77
What is frequency of gamma ray?
10^-12
78
Interference
The formation of poitns of cancellation and reinforcement where 2 coherent waves pass each other
79
Coherence
waves having constant phase difference
80
Stationary wave
A stationary wave is formed when two progressive waves of the same frequency, amplitude and speed that are travelling in opposite directions superpose. Stationary waves store energy.
81
Node
Region of destructive superposition
82
Antinode
Region of maximum constructive superposition
83
Diffraction
The spreading of waves as they pass through a narrow slit
84
What is the equation for double slit interference?
```
lambda = ax/D
a = split separation
x = width of gap
D = distance from slit to screen
```
85
What is the equation for diffraction grating?
```
d sin (theta) = n x lambda
d= distance between successive slits
= reciprocal of number of lines per meter
theta = angle from horizontal equilibrium
n= order number
```
86
What happens to a positive charge in an electric field?
Positive charge moves in the direction of the electric field; they gain Ek and lose Ep
87
What happens to a negative charge in an electric field?
Negative charge moves in opposite direction of the electric field: they lose Ek and gain Ep
88
Electric field strength
Force per unit of charge acting at a point. F/q or V/d
F is the force and q is the charge
V is p.d. and d is distance between parallel plates
89
Electric current
Flow of charged particles
90
Charge
Product of the current at that point and the time for which the current flows Q= I x t
91
Coulomb
Charge flowing per second pas a point at which the current is one ampere
92
Potential difference
The work required to move a certain coulomb of charge between two points.
93
Power
I x V
94
Ohm's law
V = IR
95
Current carrying conductors - formula?
```
I = (nLAq) / (L/v)
L = length of conductor
A = cross-sectional area of conductor
n = no. of free electrons per unit volume
q = charge on one electron
v = average electron drift velocity
```
96
What is the relationship between I and V for a metallic conductor?
Linear - V is proportional to I
97
What is the relationship between I and V for a filament lamp?
As volts go up the temperature goes up. This increases the vibration of ions, increasing the collisions of ions with electrons. This increases resistance. Straight line then curves off at the top
98
What is the relationship between I and V for a thermistor
As the voltage goes up, the temperature goes up. This releases electrons reducing resistance. Resistance which is V/I increases. Starts off straight and gradient gets steeper and steeper
99
What is the relationship between I and V for a diode
Low resistance in one direction and infinite resistance to the left of the origin - I = 0
100
Resistivity
R = pL/A
101
e.m.f.
The energy converted into electrical energy from other forms when a current passes through the power source.
102
Internal resistance
```
Resistance to current flow within the power source.
Voltage across resistor = V= IR
Voltage lost to internal resistance V=Ir
Therefore e.m.f.
E= IR + Ir
E= I(R + r)
```
103
Kirchhoff's second law
The sum of emfs in a closed circuit is equal to the sum of potential differences.
104
Kirchhoff's first law
The sum of currents entering a junction is equal to the total sum of currents leaving a junction
105
Thermistor
A type of potential divider. Resistance decreases with increasing temperature.
106
Light Dependent resistor
Resistance decreases with increasing light intensity.
107
Potentiometer
A continuosly variable potential divider used to compare potential differences. Potential difference along the wire is proportional to the length of the wire.
108
What are the results of Rutherford's gold scattering experiment?
A beam of alpha particles were fired at a thin gold foil:
- most particles pass straight through
- some are scattered slightly
- very few deflect at an angle greater than 90
Conclusion:
- All mass and charge concentrated in the centre of the atom
Nucleus is positively charged as a-particles are repelled
109
Isotope
Atoms of the same element with a different number of neutrons but the same number of protons
110
Random (radioactivity)
Impossible to predict and each nucleus has the same probability of decaying per unit time
111
Spontaneous (radioactivity)
Not affected by external factors such as the presence of other nuclei, temperature and pressure
112
Features of an alpha particle
-Helium nucleus
-42He (symbol)
+2 charge
4 relative mass
slow speed
penetration can be stopped by paper
highly ionizing
effect of magnetic field causes particle to deflect slightly
effect of electric field causes particle to attract to negative
113
Features of a beta particle
```
two types - positron B+ and electron B-
0-1e 0+1e
-1 charge and +1 charge
Fast movement speed
can be stopped by few mm of aluminium
low ionisation energy
deflected greater by magnetic field than alpha particles
attracted to opposite charge of the particle
```
114
Features of gamma radiation
```
electromagnetic
no charge
no mass
speed of light
few cm of lead
very low ionisation power
unaffected by electric and magnetic fields
```
115
a-decay
Loses a helium proton
116
B- decay
Neutron turns into a proton and an electron. An electron (0-1e) and antineutrino (00v with a line over it) are emitted
117
B+ decay
proton turns into a neutron and a positron. An electron and neutrino are emitted. neutrino shown by v with no line
118
Gamma decay
A nucleus changes from a higher energy state to a lower energy state through the emission of electromagnetic radiation ( protons)
119
Fundamental particle
a particle that cannot be split up into anything smaller
120
Quarks
Quarks are fundamental particles that make up protons and neutrons.
121
Up Quark charge?
u - +2/3
122
Down Quark charge?
d -1/3
123
Strange Quark charge?
s -1/3
124
Antiparticle
All quarks have antiparticles. The charge is just the opposite
125
Leptons
A part of elementary particles- electron family is part of this group. Electrons, positrons, antineutrinos and neutrinos
126
Hadrons
Part of composite particles. Hadrons ---> baryones ---> protons and neutrons
