Physics Definitions

Question 1

Note what is meant by the ‘Elastic Limit’ of a spring

Answer 1

The maximum load the spring can experience and still return to its original length when the deforming force is removed

Question 2

Define strain and state it’s expression and unit

Answer 2

Strain is the ratio of the change in length of a specimen to its original length
It’s expression is ε
It does not have a unit

Question 3

Define Young’s Modulus and state it’s expression and unit

Answer 3

Young Modulus is a measure of the stiffness of a material, it is the ratio of stress to strain within the limit of proportionality
It’s expression is E
It’s unit is Nm^-2 or Pa

Question 4

State Hooke’s Law and it’s equation

Answer 4

The extension of a spring, x, is directly proportional to the force applied, F, provided the limit of proportionality is not reached/exceeded

F=kx

Question 5

Define the term “Limit of Proportionality”

Answer 5

The point beyond which Hooke’s Law is no longer true when stretching a material

Question 6

Define Stress and state it’s expression and unit

Answer 6

The applied force per unit area of cross section
It’s expression is σ
It’s unit is Nm^-2 or Pa

Question 7

State Charles Law

Answer 7

For a fixed mass of gas at a constant pressure, the volume is directly proportional to the temperature in Kelvin
V/T=k

Question 8

State Boyles’ Law

Answer 8

For a fixed mass at constant temperature, the volume is inversely proportional to the applied pressure.
pV=k

Question 9

State the Pressure Law

Answer 9

For a fixed mass of gas at constant volume, the pressure is directly proportional to the temperature in Kelvin
P/T=k

Question 10

Define Ultimate Tensile Strength

Answer 10

The maximum stretching force per unit area without the material breaking

Question 11

Define Mole

Answer 11

The mole is the amount of substance which contains as many particles as there are in 0.012kg of carbon 12

Question 12

Define microscopic

Answer 12

Small scale

Question 13

Define Macroscopic

Answer 13

Large scale

Question 14

Define Isothermal

Answer 14

Constant temperature

Question 15

What is STP

Answer 15

Standard temperature and pressure, taken as 0 degrees Celsius and 1x10^5 Pa

Question 16

Define Specific Heat Capacity

Answer 16

The thermal energy required to raise the temperature of a body of mass 1kg by 1K

Question 17

Define Centripetal

Answer 17

Centre seeking

Question 18

Define Angular Velocity

Answer 18

The Rate of change of angular displacement

Question 19

What happens to a system undergoing Simple Harmonic Motion?

Answer 19

In SMH the acceleration is directly proportional to the displacement and is always directed towards the fixed position

Question 20

What is Damping

Answer 20

A resistive force which opposes motion and so causes the amplitude of a system to decrease

Question 21

How does Resonance occur

Answer 21

Resonance occurs when a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies

Question 22

What are Free Vibrations

Answer 22

Vibrations in which no energy is transferred to or from the system, thus amplitude remains fixed

Question 23

What are Forced Vibrations

Answer 23

When a system is forced to oscillate at the frequency of an external oscillator (giving it energy) it undergoes forced vibrations

Question 24

What is an Isotope?

Answer 24

Isotopes are atoms of an element with the normal number of protons and electrons, but different number of neutrons

Question 25

Define Ionisation

Answer 25

Converting a substance into an ion or ions, typically by removing one or more electrons

Question 26

Define Background Radiation

Answer 26

The ionising radiation present in the environment

Question 27

Define Exponential Decay

Answer 27

Decay in which the amount falls by a fixed fraction per unit time

Question 28

Define Activity

Answer 28

The number of disintegration’s per second in a sample, measured in Bq

Question 29

What is a Decay Constant

Answer 29

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

Question 30

What is a Half-Life

Answer 30

The time for the number of radioactive nuclei present to decay to half its original value

Question 31

Define Nucleon

Answer 31

Any constituent that exists in the nucleus

Question 32

Define Unified Atomic Mass (u)

Answer 32

1/12 of the mass of one atom of carbon 12, u = 1.66 x 10^-27kg

Question 33

What is an Electron Volt (eV)

Answer 33

A unit of energy equal to the work done on an electron in accelerating it through a potential difference of 1 volt, 1eV = 1.6 x 10^-19 J

Question 34

Define Binding Energy

Answer 34

The energy required to split up a nucleus into its constituent nucleons

Question 35

What is Binding Energy per Nucleon

Answer 35

The average energy required to completely remove a single Nucleon from its nucleus

Question 36

Define Mass Defect

Answer 36

The difference between the mass of the separated nucleus and the combined mass of the nucleus

Question 37

Define Nuclear Fission

Answer 37

The splitting of a heavy / large nucleus into lighter nuclei with the release of energy

Question 38

Nuclear Fusion

Answer 38

The joining of 2 light nuclei to form 1 heavier more stable nucleus which releases energy

Question 39

What conditions are required for Fusion?

Answer 39

The nuclei must be confined within a finite volume at a sufficient temperature to increase the chances of collision with sufficient energy to overcome the electrostatic repulsion