Definitions U1

Question 1

Hookes law

Answer 1

The extension of a spring is directly proportional to the force acting on it up to the limit of proportionality

Question 2

Stress

Answer 2

Applied force per unit area of cross section

Question 3

Ultimate tensile stress

Answer 3

Max stretching force per unit area without material breaking

Question 4

Strain

Answer 4

Ratio of change in length to original length of specimen

Question 5

Young’s modulus

Answer 5

Measure of stiffness of material, got by ratio of stress divided by strain

Question 6

Microscopic

Answer 6

Small scale

Question 7

Macroscopic

Answer 7

Large scale

Question 8

Isothermal

Answer 8

Constant T

Question 9

Boyles law

Answer 9

For fixed mass of gas at constant T the V is inversely proportional to the p

Question 10

Charles law

Answer 10

For fixed mass of gas at constant pressure V is directly proportional to the T in Kelvin

Question 11

Pressure law

Answer 11

For fixed mass of gas at cons V the p is directly proportional to the T in kelvin

Question 12

Mole

Answer 12

Amount of substance which has as many particles as there are in 12g of C-12

Question 13

Specific heat capacity

Answer 13

Thermal energy required to raise the T of a body of mass 1kg by 1K

Question 14

STP standard temperature and pressure

Answer 14

0 degrees Celsius
1x10 ^5 Pa

Question 15

Centripetal

Answer 15

Centre seeking

Question 16

Angular velocity

Answer 16

Rate of change of angular displacement

Question 17

Simple harmonic motion

Answer 17

Acc is directly proportional to the displacement
Acts towards fixed position

Question 18

Damping

Answer 18

Resistive force which opposes motion and so causes the amplitude to decrease

Question 19

Resonance

Answer 19

External force drives another to oscillate with greater amplitude at specific frequencies

Question 20

Free vibrations

Answer 20

No energy transferred to or from system, amplitude is fixed

Question 21

Forced vibrations

Answer 21

Forced to oscillate at frequency of external oscillator

Question 22

Isotope

Answer 22

Atoms of element with same number of protons but different number of neutrons

Question 23

Ionisation

Answer 23

Converts atom, molecule or substance into ion(s) by removing 1 or more electrons

Question 24

Background radiation

Answer 24

Ionising radiation present in the environment

Question 25

Exponential decay

Answer 25

Decay that falls by fixed fraction per unit time

Question 26

Activity

Answer 26

Number of degradations per second in sample, measured in Bq

Question 27

Decay constant

Answer 27

The fraction of total number of nuclei present to decay per unit time

Question 28

Half life

Answer 28

Time for number of radioactive nuclei to decay to half its original value

Question 29

Unified atomic mass

Answer 29

1/12 mass of one atom of C-12 u = 1.66x10^-27

Question 30

Electron volt

Answer 30

Unit of energy equal to work done by electron accelerating it through a pd of 1V

Question 31

Binding energy

Answer 31

Energy required to split up a nucleus into its nucleon parts

Question 32

Binding energy per nucleon

Answer 32

Av energy required to remove a single nucleon from its nucleus

Question 33

Mass defect

Answer 33

Difference between mass of separated nucleus and combined mass of nucleus

Question 34

Nuclear fission

Answer 34

Splitting of large nucleus into lighter nuclei with release of energy

Question 35

Nuclear fusion

Answer 35

Joining of 2 light nuclei to form one heavier more stable nucleus which releases energy

Question 36

Conditions required for fusion

Answer 36

Nuclei must be confined within a finite Volume at sufficient temperature to increase chances of collision with enough energy to overcome the electrostatic repulsion

Question 37

D-T reaction

Answer 37

2,1 H + 3,1 H -> 4,2 He + 1,0 n + 17.6MeV

Question 38

Internal energy

Answer 38

Sum of ke and pe in a molecule

Question 39

Kinetic theory ideal gas assumptions F e v V t

Answer 39

No intermolecular forces V and t are negligible v is constant Energy is conserved as collisions are elastic

Question 40

Critical size, what should be greater than the critical size? What should be less than the critical size?

Answer 40

Minimum size of nuclear fuel to sustain a chain reaction Total amount of fuel Amount of fuel in each rod

Question 41

Moderation

Answer 41

Slows fission neutrons (doesn’t absorb them) so that U-235 absorbs them

Question 42

Control rods Material

Answer 42

Inserted to control number of neutrons that are able to cause further fission Boron/Cadmium

Question 43

Cooling system (substance)

Answer 43

Water or CO2 is circulated around the fuel rods to cool them. Energy is passed to a heat exchanger where it is used to power a steam turbine

Question 44

Reactor shielding (material)

Answer 44

Thick steel and several metres of concrete surround reactor, preventing harmful radiation from escaping