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50 Cards in this Set

  • Front
  • Back

Define drag force

Force of fluid resistance on an object moving through the liquid

Name the factors that affect drag force

- Shape


- Speed


- Viscosity of the fluid


- Weight

Define centre of gravity

The point in an object where weight of the object appears to act

Define scalar

A quantity that has magnitude only and no direction

Why is stopping distance in practice shorter than the calculated?

- Friction is acting


- Increases resultant force which opposes motion


- Higher deceleration


- Energy lost as thermal/heat

Define moment of a force about a point

- Force x perpendicular distance


- From the line of action of the force to the pivot

Define vector

Any physical quantity that has a direction as well as a magnitude

Define displacement

Distance in a given direction

Define velocity

Speed in a given direction

State the principle of moments

In an equilibrium system, the sum of the clockwise moment is equal to the sum of the anticlockwise moment

Define centre of mass

The point through which a single force on the body has no turning effect

Define a couple

Pair of equal and opposite forces acting on a body but in opposite directions

Define torque

The moment of a couple

For a body in equilibrium,

- The resultant force must be zero. If there are only three forces, they must form a closed triangle


- The principle of moments must apply (i.e. the moments of the forces about the same point must balance out

Define speed

Change of distance per unit time

For an object moving at constant speed, its graph of distance against time is...

A straight line with a constant gradient

Define acceleration

Change of velocity per unit time

Area under the line of a speed-time graph

is equal to the distance travelled

Investigation of the free fall of a ball

- Vertical ruler to provide a scale


- Make a video clip of the ball's flight


- Rerun the clip at slow speed with the time displayed


- To obtain a multiflash photo, an ordinary camera with a slow speed shutter may be used to record the ball's descent in a dark room illuminated by a stroboscope (a flashing light)


- Flashing light to flash at a know constant rate (about 20 flashes per sec)


- Measure the time of descent and distance fallen by the ball for each image of the ball on the photograph


- The photograph shows the ball speeds up as it falls, because it travels further between successive images


- Plot graph of s against t^2


- G would be gradient x 2 since s=1/2at^2


- Use electronic timer or motion sensor to improve the accuracy of the reading of the distance fallen and time taken.

Explain why, in practice, the ball will not travel this far before hitting the ground

- Air resistance or drag


- Causing (horizontal/vertical) deceleration/ slow down

State and explain one reason why the core of an optical fibre is made as narrow as possible

- To reduce multipath/multimode dispersion


- (Which would cause) light travelling at different angles to arrive at different time/pulse broadening/poor resolution/lower transmission rate


or


- Prevent light/data/signal loss (from core/fibre)


- (Which would cause) signal to get weaker/crossover/date to be less secure

One application and benefit of optical fibres

- Endoscope/arthroscope/communications


- Improve medical diagnosis/improve transmission of data/high speed internet


State one way to raise the fundamental frequency of vibration of a guitar string

- Decrease length/increase tension/tighten string

State what is meant by monochromatic

Single wavelength/frequency

State what is meant by coherent

(wave/source have) constant phase difference

The monochromatic laser is replaced by another laser emitting visible light with a shorter wavelength. State and explain how this will affect the spacing of the maxima on the screen.

- Maxima closer together


- Spacing is proportional to wavelength/D and S are constant therefore as λ decreases so W decreases


- Smaller wavelength means smaller path difference

Describe how to obtain, accurately by experiment, the data to determine the Young modulus of a metal wire.

- Describe/Show means of applying a load/force to a wire


- Measure original length


- Measure extension


- Measure diameter


- Extension = extension length - original length


- Use of ruler/tape measure


- Measure diameter with micrometer


- Travelling microscope used to measure ext, or wire ext measured with vernier scale(Searle's apparatus)


- Varying load/mass


- Repeat readings (of ext)


- Change in diameter monitored (with micrometer)


- Cross-sectional area A=π(D/2)^2

Advantages and disadvantages of wind power compared to fossil fuel

- No fuel cost/causes no air pollution/no CO2/renewable


- Unreliable/Varies/Causes visual pollution/noise/danger to birds/high "start up" cost

Other than electromagnetic radiation, give on example of a wave that is transverse

- Water waves in a ripple tank


- Rope


- Secondary waves

State one difference between a transverse wave and a longitudinal wave

- Transverse wave: oscillation (of medium) is perpendicular to wave travel


- Transverse wave can be polarised


- All longitudinal require a medium

State one application, other than in education, of a polarising filter and give a reason for its use.

- Polaroid gasses/sunglasses to reduce glare


- Camera to reduce glare/enhance image


- Microscope to identify mineral/rocks


- LCD displays very low power


- 3D glasses to enhance viewing experience

State Hooke's Law

- Force is directly proportional extension


- Up to limit of proportionality

Explain how 1/2 x F x extension can be derived from a graph of force against extension

- Area under graph equal to work done on spring - Which is the elastic potential energy stored


- Area of triangle 1/2 x b x h therefore 1/2 x F x extension

Describe how the pattern of single slit interference of monochromatic light would change if light of a longer wavelength was used


State two ways in which the appearance of the fringes would change if the slit was made narrower

Maxima further apart/wider




- Wider separation


- Lower intensity

Six marker stationary waves

- n nodes where there's no movement/zero amplitude


- n-1 antinodes where there's maximum amplitude


- Talk about wavelength


- between nodes and antinodes, amplitude of oscillation increases


- Waves reflect off the surface at the end of propagation


- Waves travelling in opposite directions superpose/interfere


- Waves have the same frequency and wavelength


- Always cancellation at nodes/constructive superposition at antinodes


- Energy not transferred along wave

Explain why total internal reflection will not occur when a ray travels from water to glass

(TIR) only happens when ray travels from higher n to lower n

Explain the main reason why the car does not reach this height

- (work done) by friction/drag/air resistance/resistive force


- (Energy converted) to internal/thermal energy

In order to compare the mechanical properties of two different types of metal alloy, anengineer decides to measure the Young modulus for each of them. She has a sampleof each alloy in the form of a wire. Each wire is about 1.5 m in length but they havedifferent diameters.


Describe an experimental method that she could use to obtain the data necessary toaccurately determine the Young modulus of these metals. You may wish to illustrateyour answer with a diagram. The quality of your written communication will be assessed in your answer

- Measure diameter of wires


- Use a micrometer (diameter)


- Apply range of loads or masses


- Measure original length


- Measure or calculate extension


- Metre ruler used to measure original length and extension


- Calculation of the weight of the mass


- Measure diameter in several places


- At least 7 different loads


- Repeat measurements fro the same wire (or measure whilst unloading)


- Use of a travelling microscope or Searle's apparatus


- Set square for parallax reduction

Give one possible application of the spectrometer and diffraction grating

- Analysis of light from stars


- Analyse composition of stars


- Chemical analysis


- Measuring red shift

Explain what is meant by the frequency of a wave

- Number of complete waves per second


- Number of waves/time for the waves to pass a point


- Number of oscillations per second


- 1/T with T defined as time for 1 complete oscillation

Describe the nature of a longitudinal wave

- Oscillation of particles, but not oscillation of wave


- Is parallel to the direction the wave travels


- Requires medium to travel through


- Cannot be polarised

Diffraction grating

- Find distance from screen to grating (D).


- Use large value of D (>2m), repeat for different values of D for accuracy


- Measure dist between first order maximum + sub maxima (x), repeat between different order maxima


- Find angle theta between them using tan theta = x/D


-find d by calculating 1/lines per mm of grating.


- If lines per m is given, use (1/lines per m) x10^3


-use wavelength = d sin theta to find wavelength for double slit:


-Find dist between slit + screen (D) with meter rule, measure fringe separation (w) between centre of fringes with vernier scale


- Use 7+ values of w, repeat 2x and calculate mean value


- Use wavelength = ws/D (s=slit separation) to find wavelength


- Use large value of D (maybe repeat for different values of D)

Comparing white light with monochromatic

- Intensity of monochromatic (eg laser) greater than white light


- Monochromatic produces dots on screen, white light produces central white maximum then subsidiary maxima are spectra with blue closest to centre and red furthest


- Laser is coherent so wavelength/freq are constant so no spectra)


- Where waves are in antiphase there are dark fringes for both white and monochromatic light


- Laser light diverges very little compared to white light

Rifle B is fired and the bullet emerges with a smaller horizontal velocity than the bullet from rifle A


Explain why the horizontal distance travelled by bullet B will be less than Bullet A

- Vertical motion is independent of horizontal motion


- Downward/vertical acceleration is the same for both


- Acceleration due to gravity is the same for both


- Vertical velocity is the same for both


- Both bullets will be in the air for the same amount of time


- Horizontal acceleration is zero


- Distance is proportional to horizontal speed


- S=ut where u is the horizontal velocity

A steel ball is released from rest into a container of water.


- Explain how velocity and acceleration of ball vary with time


- Reference to how Newton's First and Second laws of motion apply in this situation

- Velocity increases


- Velocity becomes constant (terminal velocity)


- Acceleration is maximum (9.81) in the beginning


- Acceleration decreases to zero


- Weight greater than drag in the beginning (before terminal velocity)


- There's a resultant force downwards (before terminal velocity)


- Forces become equal, drag = weight


- Drag force increase with speed


- Resultant force = W - drag


- Acceleration = gradient of v against t

Plastic deformation

Permanent extension

The red laser light is replaced by a non-laser source emitting white light.


Describe how the appearance of the pattern would change

- Central white fringe


- Each/every subsidiary maxima are composed of a spectrum


- Each/every/all subsidiary maxima are composed of a spectrum


- Subsidiary maxima have violet/blue nearest central maximum OR red furthest from center


- Fringe spacing less/ maxima are wider/ dark fringes are smaller

Explain how the use of the single slit makes the light from the two slits sufficiently coherent for fringes to be observed

- Single slit acts as a single point source diffracting light into both slits


- The path lengths between the single slit and the double slits are constant/the same/fixed

Describe the change to the pattern seen on the screen when the violet laser is replaced by a green laser. Assume the brightness of the central maximum is the same for both lasers

Fringes further apart or fringe/pattern is wider

The scientist uses the same apparatus to measure the wavelength of visibleelectromagnetic radiation emitted by another laser.Describe how he should change the way the apparatus is arranged and used in order toobtain an accurate value for the wavelength.

- Increase D


- Measure across more than 2 maxima


- When D is increased then w increases


- So overall percentage error is lower/improved


or


- Repeat the reading with a changed distance D or using different numbers of fringes o measuring across different pairs of adjacent fringes