Physics Aqa - Unit 2 - Definitions

Front 1

A moment?

Back 1

Moment – Force multiplied by perpendicular distance between force and the pivot

Front 2

The principle of moments?

Back 2

States that for an object to be in equilibrium the sum of the anticlockwise moments equals the sum of the anticlockwise moments (no turning moment)

Front 3

An object is in equilibrium if?

Back 3

An object is in equilibrium if:

The sum of anticlockwise moments = sum of clockwise moments

All vertical forces cancel and all horizontal forces cancel

Front 4

A Couple?

Back 4

A Couple – A pair of opposite and equal forces separated by distance d, acting about point p, the turning effect at point p is equal to one of Forces multiplies by the perpendicular distance between the forces

Front 5

Centre of mass?

Back 5

Centre of mass – Where all of an objects mass appears to act about and moments cancel

Front 6

A Newton?

Back 6

A Newton – Force required to accelerate 1kg by 1ms-2

Front 7

A Joule?

Back 7

A Joule – Work done 1N through a distance of 1m in direction of force

Front 8

Law of conservation of energy?

Back 8

Law of conservation of energy – energy is never created or destroyed just converted between different types

Front 9

Hooke’s Law?

Back 9

Hooke’s Law – The extension of a spring is proportional to the force applied to it as long as the limit of proportionality is not exceeded

Front 10

Stress?

Back 10

Stress – Force per unit area

Front 11

Strain?

Back 11

Strain – Ratio of extension to original length

Front 12

Young’s Modulus?

Back 12

Young’s Modulus – Stiffness constant of a material

Front 13

A longitudinal Wave?

Back 13

A longitudinal Wave – a propagating wave with oscillations in the same direction as propagation/energy transfer

Front 14

A transverse wave?

Back 14

A transverse wave – A propagating wave with oscillations perpendicular to the direction of propagation

Front 15

A stationary wave?

Back 15

Stationary wave – Formed when 2 waves of similar frequency travelling in opposite directions interfere and the resultant wave is the vector sum of each waves displacements at that point by the principle of superposition

Front 16

Diffraction?

Back 16

Diffraction – Spreading out of a wave when passed through a slit of around an obstacle

Front 17

Coherent Sources?

Back 17

Coherent Sources – Same frequency and constant phase relationship

Front 18

Constructive Interference occurs when?

Back 18

Constructive Interference occurs – 2 waves intersect and interfere through principle of superposition and the resultant displacement I the vector sum of the 2 waves displacement at that point and the phase difference between the 2 waves at that point is a whole number of wavelengths (destructive when 180 degrees phase difference – half number of wavelengths)

Front 19

Differences between single and double slit diffraction?

Back 19

Differences between single and double slit diffraction:

Single – Wide central maxima 2x width of others and reduction in intensity going away

Double – Same intensity same width going out

Front 20

Newton's First Law?

Back 20

Newton's First Law- A body will state in the state of rest or Uniform motion unless acted upon by an external unbalanced force/resultant force

Front 21

Newton's Second Law?

Back 21

Newton's Second Law- F=ma Force is directly proportional to the mass

Front 22

Newtons Third Law?

Back 22

Newtons Third Law - Action force is always equal to the reaction force but always in the opposite direction

Front 23

Define Freefall?

Back 23

Freefall is defined as the motion of an object undergoing an acceleration of 'g'

Front 24

What is friction?

Back 24

Friction is a Force which opposes motion

Front 25

What is work?

Back 25

Work is the amount of energy transferred from one form to another when a force causes movement of some sort

Front 26

What is power?

Back 26

Amount of energy transformed from one form to another per second

Front 27

If forces stretch the material they are?

Back 27

If forces stretch the material they are tensile

Front 28

If forces squash the material they are?

Back 28

If forces squash the material they are compressive

Front 29

Waves - Displacement?

Back 29

How far a point on the wave has moved from its undisturbed position

Front 30

Waves - Amplitude?

Back 30

Maximum displacement

Front 31

Waves - Wavelength?

Back 31

The length of one whole wave from crest to crest

Front 32

Waves - Period?

Back 32

The time taken for a whole vibration?

Front 33

Waves - Frequency?

Back 33

The number of vibrations per second passing a given point

Front 34

Waves - Phase difference?

Back 34

The amount by which one wave lags behind another wave, measured in radians or degrees

Front 35

A progressive wave?

Back 35

A progressive wave carries energy from one place to another, without transferring any material

Front 36

A standing wave?

Back 36

A standing wave is the superposition of two progressive waves with the same wave length, moving in opposite directions