Build or Bust

Question 1

What waves does an Earthquake have?

Answer 1

seismic waves

Question 2

What seismic waves does an earthquake have?

Answer 2

• P waves (primary)
• S waves (secondary)
• surface waves

Question 3

Where is a P wave found?

Answer 3

its a body wave so is found all over the Earth - it is the first wave felt because it travels faster as mechanical waves are able to pass on energy more easily

Question 4

Where is a S wave found?

Answer 4

its a body wave so if found all over the Earth but gets there second

Question 5

Where are surface waves found?

Answer 5

only in the Earth’s crust

Question 6

What type of waves are P and S waves?

Answer 6

P wave is a longitudinal wave

S wave is a transverse wave

Question 7

Longitudinal wave

Answer 7

Oscillation of particles occur parallel to the direction of travel/ wave motion/ propagation/ energy transfer. Has compressions and rarefactions

Question 8

Transverse wave

Answer 8

Oscillation of particles occur perpendicular to direction of travel/ propagation/ wave motion/ energy transfer

Question 9

Young’s modulus equation

Answer 9

Stress / strain (measured in Nm^-2) could be Fl/Ax

Question 10

What is Young’s modulus?

Answer 10

how much force is needed to make the 1x1x1 cube stretch by a certain amount

Question 11

Find Young’s modulus of a material experiment

Answer 11

IV - force
DV - cross sectional area, original length, extension
Get a material measure the length of it and the cross sectional area. Use clamp, desk pulley, markers and metre ruler. Hang off edge of table, add force to hanging end and note how much a marker moves (this is the extension) Plot a graph of stress against strain, work out the gradient

Question 12

What is the shadow zone?

Answer 12

the area waves aren’t felt

Question 13

What material can’t transverse waves travel through very well?

Answer 13

transverse can’t travel through liquid very well (this includes S waves through the outer core)

Question 14

Free oscillation

Answer 14

if an object is set vibrating it will oscillate at its natural frequency

Question 15

Seismometer

Answer 15

earthquake is driver so we want the seismometer to have the same natural frequency

Question 16

Amplitude

Answer 16

furthest distance from equilibrium (maximum point away from zero point)

Question 17

How to measure the time period of a pendulum/ spring

Answer 17

• displace pendulum (only a small displacement)
• measure the time for 20 oscillations
• full oscillation is time between passing the same point in the same direction (always measure from the mean position)
• divide by 20 for time period of one oscillation

Question 18

How can we reduce error when measuring period of pendulum?

Answer 18

• to reduce parallax error use a Fiducial marker - 2 posts, put pendulum between them
• increase overall oscillations measuring 20 instead of 10 or 30 instead of 20 this reduces uncertainty

Question 19

How can you make a wine glass break?

Answer 19

Hit the wine glass once, it will oscillate at its natural frequency, if you match this frequency and hold it the glass will break. This is because maximum energy transfer is occurring so it won’t be able to withstand oscillations so will crack and then break

Question 20

If the driver frequency equals the natural frequency…

Answer 20

…resonance will occur

Question 21

What happens to the amplitude when resonance occurs?

Answer 21

the amplitude increases dramatically

Question 22

Natural frequency

Answer 22

The frequency an object oscillates at when hit into motion. When driven at this frequency there will be violent movement. Also maximum amplitude occurs when maximum energy transfer happens because the natural frequency of the driver is the same as the driven

Question 23

Resonance

Answer 23

• when an object oscillates at its natural frequency

- if driven at this frequency amplitude will get bigger due to maximum energy transfer

Question 24

Simple harmonic motion

Answer 24

Pull pendulum to one side, force pulling back to mean position. The further from mean position, bigger force pulling it back to equilibrium.
Force is proportional to displacement (from original position)
Displacement is proportional to acceleration

Question 25

Object undergoing SHM

Answer 25

- acceleration proportional to displacement from equilibrium position - acceleration in opposite direction to displacement

Question 26

Equations for SHM

Answer 26

``` F = -kx a = -kx ```

Question 27

Where is the force directed in SHM?

Answer 27

force is always directed towards the mean position

Question 28

In SHM the period is...

Answer 28

independent of the amplitude

Question 29

Energy when pendulum at equilibrium

Answer 29

Potential energy = 0 | Kinetic energy = max

Question 30

Energy when pendulum at max amplitude

Answer 30

Potential energy = max | Kinetic energy = 0

Question 31

2 springs in parallel =

Answer 31

double stiffness

Question 32

The total amount of energy in the system of a simple harmonic oscillator is...

Answer 32

...constant - the kinetic and potential energy values change but the total energy doesn't

Question 33

How can sound waves moving through a material be modelled?

Answer 33

as simple harmonic motion

Question 34

Stiffer material =

Answer 34

greater wave velocity through it

Question 35

Why does sound travel faster through hotter air?

Answer 35

because it has a lower density

Question 36

brittle

Answer 36

no plastic deformation before it cracks

Question 37

Fixed points

Answer 37

melting point of ice boiling point of water triple point of water

Question 38

Specific Heat capacity

Answer 38

the amount of energy required to raise 1kg by 1K (or degrees celsius)

Question 39

What happens to the oscillations when damping occurs?

Answer 39

oscillations reduce over time

Question 40

What causes damping?

Answer 40

normally due to friction or resistance

Question 41

Latent heat

Answer 41

- energy required to change the state of 1kg (or g) of an object - change the intermolecular bonds (increase potential energy of particles or energy given out) - energy involved in a phase change

Question 42

Conduction

Answer 42

'spreading' through the material by atomic and molecular vibrations and motion of free electrons

Question 43

Convection

Answer 43

heating of a fluid, expands when heated, becomes less dense so rises, cooler denser fluid takes its place creating a convection current

Question 44

Radiation

Answer 44

energy lost by electromagnetic radiation, hotter object, shorter wavelength of emitted radiation

Question 45

What is needed to produce a phase change?

Answer 45

energy

Question 46

What is a phase change?

Answer 46

a change in state e.g. solid --> liquid or liquid --> gas

Question 47

Phase change materials

Answer 47

objects change state at certain temperatures

Question 48

Internal energy

Answer 48

sum of potential and kinetic energy in a group of particles

Question 49

What happens to the internal energy during a phase change?

Answer 49

during a phase change the internal energy will change

Question 50

TMD

Answer 50

tuned-mass damper

Question 51

What is an effective way to reduce resonance within a building?

Answer 51

to have a TMD

Question 52

What does a TMD do?

Answer 52

add massive pendulum or spring mass system that has the same natural frequency as the building -If the building is driven to oscillate at same frequency, both structure and TMD will resonate. The TMD will oscillate in antiphase so amplitude of oscillations reduced

Question 53

Damping

Answer 53

-the amplitude of oscillations in a system that is not subject to an external driving force will decrease over time due to resistive forces within the system

Question 54

What is damping a consequence of in mechanical systems?

Answer 54

friction or viscous drag

Question 55

What do dampers do?

Answer 55

dissipate the energy

Question 56

Light damping

Answer 56

- amount of energy lost within each oscillation is quite small - system oscillates several times before rest (swing door, oscillates several times before shutting)

Question 57

Critical damping

Answer 57

-something moves back to its equilibrium position as fast as possible but never quite beyond it

Question 58

Heavy damping

Answer 58

-the system takes a long time to return to equilibrium position then stays there without oscillating (door with stiff hinges, closes slowly)

Question 59

Heavier the damping...

Answer 59

...the quicker energy is lost from that system

Question 60

Damped system

Answer 60

absorb energy and vibrate when driven but resonate vibrations have smaller 'spread' over wide frequency range

Question 61

Damping can make an oscillating system come to rest more quickly, it can also...

Answer 61

...prevent it from resonating quite so violently when driven at its natural frequency