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let's get physical! > CPACs > Flashcards

CPACs Flashcards

1
Q

determine the acceleration of a freely falling object

A
  1. set of two light gates to measure time and and an electromagnet on a stand
  2. measure the distance between the light gates
  3. release the steel ball from the electromagnet
  4. repeat for different distances between the light gates
  5. using s = ut + 1/2at^2 plot 2s/t agaisnt t. The gradient is the acceleration
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2
Q

determine the acceleration of a freely falling object control variables

A
  • The distance from the point of release and the first light gate
  • the mass of the object / the object
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3
Q

Why use and electromagnet in ‘determine the acceleration of a freely falling object’

A

It means there is no force of propulsion so SUVAT can be used

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4
Q

risks in ‘determine the acceleration of a freely falling object’

A
  • falling objects, put padding on the falling region

- tall unstable object, clamp to the table

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5
Q

Sources of uncertainty in ‘determine the acceleration of a freely falling object’

A
  • make sure the ruler is exactly vertical

- normal resolution uncertaintities

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6
Q

Determine the electrical resistivity of a material

A
  1. Set up the wire in a circuit with an ammeter in series and a voltmeter in parallel
  2. measure the diameter of the wire using a micrometer and calculate its area
  3. measure the length of wire used in the circuit
  4. measure the current and voltage
  5. calculate the resistance of the wire
  6. repeat for different lengths
  7. plot a graph of R agaisnt 1/L
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7
Q

Determine the electrical resistivity of a material control variables

A
  • material of the wire

- power supply

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8
Q

Determine the electrical resistivity of a material sources of uncertaintity

A
  • measure diameter of wire (measure at 3 different points +check for zero error first)
  • don’t leave power supply on at it heats up and effects equation
  • regular resolution uncertainties
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9
Q

Determine the electrical resistivity of a material risks

A
  • electricity, check equipment is in good condition

- cut wire, be aware of the sharp wire

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10
Q

Determine the emf and internal resistance of an electrical circuit

A
  1. set up a variable resistor, ammeter and switch in series with a voltmeter in parallel over the supply.
  2. measure the pd and current for different resistances
  3. plot V agaisnt I, the emf is the y intercept and the internal resistance is the gradient
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11
Q

emf =

A

V + Ir

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12
Q

Determine the emf and internal resistance of an electrical circuit hazards

A
  • electricity, check equipment is in good condition

- heat/burning, disconnect wire between readings

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13
Q

Use a falling ball method to determine the viscosity of a liquid

A
  1. measure the mass of the ball and the volume (measure how much water it displaced) then calculate the density
  2. place two rubber bands on the tube which allows for a good time interval of the object moving at terminal velocity
  3. drop the ball and measure the time it takes to get from the first band to the second
  4. measure the distance between the rubber bands
  5. calculate the density of the fluid
  6. calculate viscosity using the gathered information
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14
Q

How do you measure the volume of an object

A

measure how much water it displaces

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15
Q

Use a falling ball method to determine the viscosity of a liquid control variables

A
  • drop the ball as close to the surface of liquid as possible
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16
Q

Viscosity =

A

(2r^2g(density of ball - density of fluid))/9v

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17
Q

Use a falling ball method to determine the viscosity of a liquid sources of uncertaintity

A
  • may be errors in the human reaction time

- uncertaintity due to resolutions

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18
Q

Use a falling ball method to determine the viscosity of a liquid risks

A
  • split liquid, clean up spills immediately + keep tube away from the edge
  • elastic bands, wear safety goggles + don’t play with the bands
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19
Q

Determine the young modulus of a material

A
  1. measure the diameter of the wire. Measure the original length of the wire.
  2. attach the wire to the desk and thread it over a pulley with hanging masses on the end. Put a sticky label on the wire at the end of the metre ruler.
  3. Add the masses to the hanger and record the distance movement of the sticky marker.
  4. plot extension against the weight (mg). The gradient is equal to length/area*young modulus.
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20
Q

Determine the young modulus of a material sources of uncertainty

A
  • measure the diameter 3 times and take an average
  • measure the masses individually and don’t just use the value given on the mass
  • regular resolution uncertainties
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21
Q

Determine the young modulus of a material sources of uncertainty risks

A
  • wire under strong force, wear safety goggles and make a paper bridge to go over the wire and absorb the energy from the wire
  • hanging masses, mark the area where it falls and avoid it
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22
Q

Young modulus =

A

stress / strain = Fl / Ae

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23
Q

Determine the speed of sound in air using a 2-beam oscilloscope, signal generator, speaker and microphone

A
  1. Set up an oscilloscope with a signal generator and speaker a set distance from the microphone.
  2. turn the signal generator on. Adjust the oscilloscope to show 3 wave cycles.
  3. adjust the spacing between the microphone and the speaker until the waves line up. The measure the distance between.
  4. move the speaker until the trace has moved exactly one cycle along and measure this distance.
  5. the difference between these distance is the wavelength
  6. calculate the frequency by measuring the time period from the trace
  7. calculate the velocity by using v = fλ
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24
Q

Determine the speed of sound in air using a 2-beam oscilloscope, signal generator, speaker and microphone sources of uncertaintity

A
  • the image on the oscilloscope is likely to be unclear/ rapidly changing leading to a higher uncertaintity
  • normal resolution uncertaintities
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25
Q

Determine the speed of sound in air using a 2-beam oscilloscope, signal generator, speaker and microphone risks

A
  • high frequency sounds, only leave it one for when it is needed to avoid discomfort
  • electrical appliances, check its in a condition safe to use
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26
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string or wire method 1

A
  1. Attach a string to a vibration generator and thread it through a bridge and over a pullet with 100g of masses attached to the end
  2. turn on the signal generator and vary the frequency until the string oscillates at its fundamental frequency. record this frequency.
  3. repeat this for 200g, 300g 400g and 500g
  4. calculate the tensions in the string (T = W = mg)
  5. calculate how the wave speed changes with different tensions v= √(T/μ)
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27
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string or wire method 2

A
  1. Attach a string to a vibration generator and thread it through a bridge and over a pullet with 100g of masses attached to the end
  2. turn on the signal generator and vary the frequency until the string oscillates at its fundamental frequency. record this frequency, record the distance from the signal generator to the bridge.
  3. repeat for different lengths between the signal generator and bridge
  4. plot a graph of λ agaisnt 1/f the gradient is the wave speed
28
Q

how to calculate mass per unit length

A

Take 1m of the string and weigh it

29
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string or wire why different methods

A

Because its an investigation that finds relationships between a variable and the wave speed

30
Q

Determine the wavelength of light from a laser using a diffraction grating

A
  1. place the laser a measured distance from the wall
  2. place the diffraction grating between the wall and laser.
  3. mark the points of zero order and first order maxima. measure the distance between n=0 and n=1
  4. using the two distances calculate θ using trigonometry
  5. using dλ = dsinθ work out λ
31
Q

Determine the wavelength of light from a laser using a diffraction grating sources of uncertaintity

A
  • measure the distance from n=0 to n=1 either side then take an average
  • regular resolution uncertainties
32
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string or wire control variables

A
  • when investigating tension keep length constant and vice versa
  • same type of string
33
Q

Determine the wavelength of light from a laser using a diffraction grating hazards

A
  • lasers, don’t shine them into eyes or on reflective - surfaces
  • electricity, check apparatus is is suitable condition
34
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string or wire hazards

A
  • hanging masses, mark falling area and don’t stand there
  • wire under tension, wear goggles to protect eyes
  • electrical equipment, check apparatus is a suitable condition
35
Q

Investigate the relation between the force exerted on an object and its change of momentum

A
  1. set up a trolley attached to masses by a string threaded over a pulley on a tilted ramp. add a light gate near the bottom of the ramp.
  2. release the trolly from the top of the slope. Recording the distance to the light gate, the hanging masses, time taken to get to the light gate and the velocity at the light gate.
  3. repeat for different masses
  4. plot mt agaisnt v. The gradient should equal g. compare the calculated value to the actual value.
36
Q

momentum equation rearrange for question

A 
Ft = mv - mu 
mgt = mv
37
Q

Investigate the relation between the force exerted on an object and its change of momentum risks

A
  • hanging masses, keep feet away for falling area

- moving trolley, make sure people are away when youre about to complete the test

38
Q

Investigate the relation between the force exerted on an object and its change of momentum sources of uncertaintity

A
  • human reaction time when timing will cause uncertaintity

- normal resolution uncertainties

39
Q

Investigate the relation between the force exerted on an object and its change of momentum control variables

A
  • angle of slope
  • distance between release and light gate
  • trolley mass/ wheel material
  • string elasticity
40
Q

Investigate the relation between the force exerted on an object and its change of momentum Why make the track a slope?

A

to counteract the effect of friction

41
Q

Use ICT to analyse collisions between small spheres method

A
  1. measure the mass/diameter of spheres
  2. start recording video and roll B into sphere A
  3. repeat, varying the lines of approach so that the collision angles are different
  4. using tracker software to calculate the momentum before and after the collision
42
Q

Use ICT to analyse collisions between small spheres risk

A
  • fast moving metal spheres could hit and hurt, so don’t propell them too fast
  • getting the camera correct in the set up, could fall and hurt so don’t set it up too high
43
Q

Use ICT to analyse collisions between small spheres sources of uncertainty

A
  • can’t easily repeat measurements as its hard to achieve the exact same velocity/angle
  • regular resolution percentage uncertainty
44
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor method

A
  1. set up the circuit above with the first resistor
  2. move the switch/flying lead to charge up the capacitor
  3. record this pd and V0
  4. move the switch for the capacitor to discharge and start the stopwatch
  5. record the pd every 10 seconds
  6. plot lnV agaisnt t. the gradient is -1/RC and the y intercept is lnV0
45
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor risk

A
  • capacitor retains charge which may cause shocks/electrocution so be sure to discharge
  • high voltage open circuit could cause shocks so don’t let the voltage exceed 40v
46
Q

capacitor discharge equation

A

V = V0e^-t/RC

47
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor sources of uncertaintity

A
  • human error using a stopwatch

- resolution uncertainties

48
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor controls

A
  • resistance of resistor
  • capacitance of the capacitor
  • same wire/ battery
49
Q

Calibrate a thermistor in a potential divider circuit as a thermostat

A
  1. record the temperature of the water
  2. put the thermistor in the beaker and record the resistance
  3. repeat for a range of temperatures of water
  4. plot resistance against temperature then for an unknown temperature record the resistance and read across to find the temperature
50
Q

What type of circuit is used to Display and analyse the potential differential difference across a capacitor as it discharges through a resistor

A

potential divider circuit

51
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor risks

A
  • water + electricity could result in an electric shock
  • hot water could scald
  • glass beaker if broken could cut
52
Q

Display and analyse the potential differential difference across a capacitor as it discharges through a resistor control variables

A
  • same resistor

- same beaker so same surface area of liquid

53
Q

Determine the specific latent heat of ice method

A
  1. measure 50g of ice into the funnel and wait until it reaches 0 degrees
  2. record the mass of an empty dry beaker
  3. put 100cm^3 of water in the empty beaker and record the total mass m, and the temperature of water
  4. add the 0 degrees ice to the water beaker
  5. record the lowest temperature reached by the ice/water mixture
  6. determine the final total mass of the ice water and beaker
  7. Energy received by ice = Energy released by water
    Lm (of ice) + m (of ice)cΔθ = m(of water)CΔθ
54
Q

Determine the specific latent heat of ice risks

A
  • glass beaker could shatter and cut
  • melting ice could be a slip hazard
  • water near electrical equipment
55
Q

Determine the specific latent heat of ice sources of uncertainty

A
  • energy transferred to other places e.g. heat from room

- resolution uncertainties

56
Q

Investigate the relationship between the pressure and volume of a gas at fixed temperature method

A

either use boyles law equipment or…

  1. using a syringe fix a set mass of gas in by sealing off the end.
  2. measure the diameter of the syringe in three places, then calculate the area
  3. hang masses to change the force, measure the length the syringe increased by each time to get the volume.
  4. calculate the pressure
  5. plot pressure against 1/volume if its directly proportion it obeys boyles law
57
Q

Investigate the relationship between the pressure and volume of a gas at fixed temperature risk

A
  • high pressure so a safety screen may be neccessary + wear goggles
58
Q

Investigate the relationship between the pressure and volume of a gas at fixed temperature sources of uncertainty

A
  • Atmospheric pressure may effect the graph meaning it won’t go through (0,0)
  • resolution uncertainties
59
Q

Investigate the relationship between the pressure and volume of a gas at fixed temperature control variables

A
  • speed of pumping may cause heating if done too fast
60
Q

Investigate the absorption of gamma rays by lead method

A
  1. measure the width of varying lead sheets using the micrometer
  2. record the background radiaion by measuring the counts in 1 minute
  3. with each sheet of lead record the counts per minute and subtract the background radiation from it
  4. plot width against ln counts the gradient is the decay constant and the y intercept is ln C
61
Q

Investigate the absorption of gamma rays by lead risks

A
  • radioactive material can be bad for health, so point the source away and do not touch
  • lead can be poisonous if enters the blood stream
62
Q

Investigate the absorption of gamma rays by lead sources of uncertainty

A
  • the further away from the source the less intense the radiation
  • resolution uncertainties
63
Q

Investigate the absorption of gamma rays by lead control variables

A
  • distance of the source from the lead

- source of radiation (and intensity)

64
Q

Determine the value of an unknown mass using the resonant frequencies of known masses on a spring method

A
  1. record the time for 10 oscillations
  2. change the mass and repeat
  3. find the time for one oscillation then square it
  4. draw a graph of T^2 against mass
  5. find the time for an unknown mass then use the graph to determine the mass
65
Q

Determine the value of an unknown mass using the resonant frequencies of known masses on a spring risks

A
  • spring could pin and hit eye so wear goggles

- masses hanging from a stand could fall so clamp to the table

66
Q

Determine the value of an unknown mass using the resonant frequencies of known masses on a spring control variables

A
  • human error so record time for 10 oscillations to reduce
  • measure masses individually with a top pan balance
  • resolution uncertainties
67
Q

Determine the value of an unknown mass using the resonant frequencies of known masses on a spring sources of uncertainty

A
  • same spring (so same stiffness)

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