Exam Questions (Redos, Techniques, Facts)

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

In an experiment which involved measuring time, a student used a stopwatch - describe how different apparatus could be used to measure the time so that the % uncertainty is reduced

Answer 5

Either use a light gate and data logger for a more accurate determination of time
Or a video camera which can be analysed frame by frame

Question 7

Describe one safety precaution when carrying out the speed of stationary wave on string practical

Answer 7

Wear suitable footwear (to protect from falling masses)
Wear safety glasses (in case teh string breaks)

Question 8

When using a micrometer, give 1 technique for measuring stuff well

Answer 8

Look at the micrometer from different orientations along the wire
As the wire diameter may not be uniform
OR
Check for 0 error
As zero error reduces the accuracy of measurement

Question 9

When describing how a vibrating string causes pressure variations in the air: how do you describe how the molecules oscillate?

Answer 9

Molecules are displaced from equilibrium positions

Question 10

Never say antibodies have larger amplitude (when describing standing waves) instead say ____amplitude

Answer 10

Maximum

Question 11

Explain why waves need to be coherent to produce a standing wave

Answer 11

Coherent means the waves have a constant phase relationship
If the relationship is not constant, a point could be sometimes constructive and sometimes destructive

Question 12

Answer 12

Question 13

If the number of slits per mm in the diffraction grating increases, does d increase or decrease?

Answer 13

d = the slit separation
So it decreases

Question 14

REMEMBER WHAT when writing your final answer

Answer 14

Units

Question 15

What do you do to ensure accuracy of an experiment (increasing the likelihood of accuracy)

Answer 15

Decrease % uncertainty
(By increasing measumrent size or increasing resolution)

Question 16

Things with longer ___ diffract more

Answer 16

Wavelengths

Question 17

What is the unit of sin theta - how should you write the units for sin theta?

Answer 17

Sin (theta/little zero for degrees)

Question 18

How can you check whether a diffraction grating with a certain spacing is appropriate to measure d sin theta = n lambda?

Answer 18

There should be a significant difference in the angles for each of the maximas

Question 19

Answer 19

• diffraction occurs when light is reflected from the CD surface
• each ring on the CD acts as a diffraction centre scattering light in all directions
• interference occurs
• in directions in which there is a phase difference equal to an even multiply of pi radians (or a who,e number of wavelengths) there is constructive interference
• white light is a range of wavelengths
• each wavelength of light reinforces in a different direction which explains why a spectrum is seen

Question 20

Criticise these results

Answer 20

Inconsistent number of decimal places for resistance (resistance should be to 3dp)
Inconsistent intervals in temperature (large jump in temperature from 38 to 55)

Question 21

Should you include units for calculations of gradients?

Answer 21

Yes

Question 22

Give 3 things you could do to improve the accuracy of measumrents of your (y intercept) or (gradient)?
(Things in brackets would be replaced with the specific context of the question)

Answer 22

• take a measurement at 0 (with units) to measure (y intercept) accurately
• take (resistance) measurements for smaller increments (of temperature) - to improve accuracy of gradient
• use a digital (thermometer) - to avoid parallax error
• take (resistance) measurements for a wider range of (temperatures) - wider range of independent variable - to improve the accuracy of the gradient

Question 23

What two errors should you be careful to avoid when using a micrometer or vernier calliper/two ways of making the experiment more accurate

Answer 23

• check for zero error
• take readings in different orientations/positions

Question 24

Describe how a student can accurately determine the radius of the first bring ring/distance to maxima point of a diffraction pattern

Answer 24

• use vernier callipers
• measure the diameter of teh first ring and divide by 2 (or distance from first order maxima on left to maxima on right and divide by 2)
• measure in multiple orientations and calculate the mean
• measure to the middle/brightest part of the ring

Question 25

Explain how a diffraction pattern (showing concentric bright rings) gives evidence for the wave nature of electrons

Answer 25

- diffraction is a wave property - the diffraction pattern is evidence the electrons have interfered

Question 26

When rearranging an equation into straight line form to explain why the line of best fit is a straight line what is it important to state

Answer 26

- that (the variables which are constants) are constants

Question 27

Explain how you could use a vernier callipers to measure the diameter of a coin accurately

Answer 27

- measure multiple coins / multiple positions/orientations on the same coin Mean diameter calculated - check and correct for zero error of the measuring device

Question 28

Explain the variation of resistance with potential difference for the filament bulb in terms of particle behaviour

Answer 28

- as pd increases the energy of electrons increases - so there is greater energy transfer in collisions with lattice ions - increasing the temperature of the metal/filament/ions - amplitude of vibrations of lattice ions increases - collision rate between lattice ions and electrons increases - due to the increase in resistance, the ratio of I/V decreases NOTE the energy transfer being greater is a significant part of the answer!

Question 29

Add the missing sentence to this answer

Answer 29

Thermistor resistance as a proportion of total resistance decreases

Question 30

Answer 30

Question 31

Discuss the suitability of each circuit to collect the data

Answer 31

(Remember to write a statement in agreement if it asks you to discuss!) - both circuits are suitable as they allow readings of pd/current for the lamp - for circuit 1 the minimum pd across the lamp is 0V when the slider is on the left - for circuit 1 the maximum pd across the lamp is the supply pd (when the slider is at the right) - for circuit 2 adjusting the resistor changes the circuit resistance (so the current is varied) - so for circuit 2 the minimum pd depends upon the resistance of the variable resistor - circuit 1 is better because it allows a bigger range, and allows pds down to 0V to be used

Question 32

Answer 32

- the battery has internal resistance - there is a pd across the internal resistance of the battery (lost volts) - terminal pd is less than emf

Question 33

How should you edit the last sentence (instead of saying overheat) to get full marks on this question?

Answer 33

It reduces the life of the remaining bulbs

Question 34

To determine cross sectional area of a wire what equipment should you use

Answer 34

A micrometer

Question 35

You need a wire to make a 3 A fuse If the actual maximum current of a fuse wire before it breaks is less than 3A does that make it suitable for use or not?

Answer 35

Yes

Question 36

What is the limit on pulse length and distance for pulse echo technique

Answer 36

- pulse length needs to be less than half distance / half pulse length needs to be less than distance - half wavelength needs to be less than distance Or wavelength needs to be less than half distance

Question 37

Explain why birds emit pulses with shorter time intervals between them when they are close to an obstacle than when they are further from an obstacle

Answer 37

- the birds needs to distinguish between received clicks, so one must be eceuved beckre the next is sent - as the bird gets closer to an obstacle more frequent updates on the position are enquired

Question 38

Explain how pulse echo location for birds works

Answer 38

- they detect the reflection of their clicks - the close an obstacle is the shorter the time interval between the clicks returning

Question 39

What is the rule for the number of dp in calculated data from addition/subtraction?

Answer 39

Same number of dp as the limiting term in the raw data

Question 40

Always say that there are 4 ____ OF RESULTS in a table rather than 4 results

Answer 40

SETS

Question 41

Give the final % uncertainty to ___ significant figures

Answer 41

One to two

Question 42

Answer 42

Question 43

Answer 43

Question 44

Answer 44

Question 45

Answer 45

Question 46

Answer 46

Question 47

Answer 47

Question 48

What is conservation of momentum?

Answer 48

Total momentum before a Collision is equal to the total momentum after a collision, provided no external force es act

Question 49

Give a reason why the ultrasound is emitted in short pulses

Answer 49

So the reflected pulse returns before next pulse is transmitted

Question 50

Answer 50

Question 51

Answer 51

Question 52

Answer 52

Question 53

What is the rule for number of dp/sf of calculated data after division or multiplication of raw data

Answer 53

Same number of sf as the limiting term (minimum number in raw data)

Question 54

What is the rule for number of dp/sf for addition/subtraction of raw data to make calculated data?

Answer 54

Number of dp of the limiting term (minimum number of dp in raw data)

Question 56

Answer 56

Question 57

Answer 57

Question 62

Answer 62

Question 63

Answer 63

Question 64

Answer 64

Question 66

How to measure diameter of a wire accurately

Answer 66

Use a micrometer , check for zero error first Measure the diameter of the wire in at least 3 different positions and orientations along the wire and then take a mean To reduce the effect of random error

Question 67

Never leave % uncertainty to more than ___sig fig

Answer 67

2

Question 68

How do you find total uncertainty in A^2 + D^2

Answer 68

When you are adding you use sum of absolute uncertainty of both

Question 70

Answer 70

Question 72

What is the change in momentum equation

Answer 72

(Final momentum - initial momentum) /time

Question 73

As speed of a vehicle increases what else increases?

Answer 73

Drag

Question 74

If a charger is charging at a lower current (or any appliance is us using a lower current) what effect is reduced

Answer 74

Heating effect

Question 75

K

Question 76

What force increases with speed? What does this mean for acceleration at high speeds

Answer 76

Air resistance It decreases

Question 78

What are 3 key things to criticise about any investigation?

Answer 78

- have they done repeats and calculated a mean? - have they checked/repeated anomalous results? - have they used small enough intervals for the independent variable?