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Physics P6 Notes
Measuring Experiment
Suggest why it is more accurate, when using a ruler, to measure diameter for five marbles .rather than measure the diameter of a single marble
effect of uncertainties reduced diameters of marbles vary Describe how the student uses the two blocks and the marble to determine a new accurate value for the diameter of a marble. Draw a diagram to show the arrangement. Describe clearly how the student ensures that the value for the diameter of a marble is as accurate as .possible
use marble between two blocks and measure gap measure gap in at least two places and check equal to ensure blocks are parallel / rotate marble to different axis and take average of measurements Pendulum Experiment Explain why timing 10 oscillations gives a more accurate result for the period T than timing 1 oscillation
Timing) errors (due to reaction time) less significant / (same) error is spread over a longer ) .time reduces the effect of (reaction) timing errors / reduces the percentage error / uncertainty / the (reaction time) error is spread over 20 oscillations
. Suggest how the procedure can be improved to increase the accuracy of the result
time a) greater number of oscillations ) Describe one technique that you use to improve accuracy when measuring the time t for 10 .oscillations
Use of fiducial point / counting from when pendulum passes the vertical / start counting from .zero Describe one technique that you use to improve accuracy when measuring the distance d. .You may draw a diagram to help your description
Use of set square or similar horizontal aid OR metre rule close to bob / pendulum
Explain how you would measure the distance d as accurately as possible. Draw a diagram to .help your explanation
diagram to show (correct use of) a horizontal aid (e.g., a set-square / ruler), matching wording measure the diameter of the bob with two blocks and a ruler / micrometer, divide by 2 to find the radius and add this on to the length of the string measure to the top and the bottom of the bob, find the average Another student suggests that T 2 is directly proportional to d. Explain briefly how to test the .suggestion using the results in Table 1.
plot a graph of T2 against d (if directly proportional) it will be a straight line passing through the origin Hooke’s Law Experiment State what additional materials the student needs to continue the experiment
More weights Density, Mass and Volume Experiment
Suggest why the value of VA (measuring dimensions multiplying them) is only an approximation of the volume of the block. Describe how the accuracy of VA can be improved
difficult to measure irregular dimensions / owtte repeat in several places (for each dimension) and take averages
. Describe briefly how a measuring cylinder is read to obtain a value for the volume of water
line of sight perpendicular / at eye level / at right angles
No, as (mass of clay) increases / changes mass of metre ruler Or Yes, as (mass of clay) only a small % of mass of metre ruler / owtte
Suggest one practical reason why it is difficult to obtain accurate readings for a and b
Difficult to obtain exact balance difficult to judge position of (centre of) load load / ruler may slide Describe the main difficulty that a student has when doing this experiment as accurately as .possible
obtaining exact balance judging position of (centre of) load masses sliding on ruler Using only the apparatus provided for the experiment, explain briefly how you would .determine the position of the centre of mass of the metre ruler
Balance rule on pivot, balance point is at centre of mass / Find where the rule balances / pivot point is read
. Describe a technique for ensuring that the ruler is as near as possible to being balanced
idea of allow to (just) tip one way then the other way / owtte
Cooling Experiment
. Explain why it is good practice to read the thermometer scale at right angles to the reading
Avoids line-of-sight / parallax error Describe two precautions that can be taken to ensure that temperature readings in the .experiment are as accurate as possible
view scale reading perpendicularly wait until readings stops rising avoid thermometer touching beaker Describe one technique to use so that the temperature reading is as accurate as possible in .this experiment
view temperature scale perpendicularly
. Explain briefly why it is good practice to read the thermometer scale at right angles
to avoid parallax error owtte
. Show the line of sight you use to obtain an accurate reading of the volume of water
Clear indication of line of sight at right angles to cylinder and level with surface of liquid. ((miniscus The student uses a measuring cylinder to measure 200cm3 of hot water. She reads the scale at right angles. Suggest another precaution to obtain an accurate reading of the volume of the water
read at bottom of meniscus OR ensure measuring cylinder is on horizontal surface The student pours an estimated volume of 75cm3 of hot water into a beaker. He uses the scale on the beaker as a guide. Suggest one possible source of inaccuracy in the procedure, .even if it is carried out carefully
cm3 difficult to estimate with large graduations on beakers 75 Another student thinks that more thermal energy is lost from the surface of the water in beaker B than from the sides of beaker B. Suggest an additional experiment that she can do with beaker B to test her idea
repeat for beaker B with lid / cover on top or with insulation on sides A student suggests that the decrease in temperature of the water in 90s should be greater when the starting temperature is greater. Suggest how you would continue the experiment, .using the same apparatus and method, to investigate the suggestion
take additional readings at times beyond 180 s for at least another 180 s / until the temperature is close to room temperature or stops decreasing
. State 2 control variables for this experiment
volume of water initial temperature material of beaker / thickness of beaker / surface area of beaker same) lids ) room temperature / appropriate environmental factor Suggest one change to the experiment to reduce the water outside the beaker form cooling .down
large(r) volume of water surrounding beaker A use of constant temperature water bath
. Suggest how to display the results to make it easier to see the trend in the rate of cooling
plot a graph of temperature against time OR cooling rate against time / temperature Suggest two changes to the experiment that the student makes to increase the rate of cooling of the hot water without changing the starting temperature of the hot water. Room .temperature remains constant
remove lid thinner lid paint the beaker black stir the water change beaker to container that is a better conductor / named metal
Suggest one precaution that can be taken to ensure measurements are accurate in this experiment
mark base of lens clamp rule to bench lens and screen upright darkened room State and explain whether your results for the focal length f are equal within the limits of experimental accuracy
Statement matches results Justification matches statement with reference to values being within 10% of each other
A student decides to continue the experiment using larger values of u. Explain why this produces less accurate values for W (h0 / h1 where h0 is the size of the object and h1 is the (size of the image
values of h1 become very small / difficult to measure or greater % uncertainty Describe one difficulty that is experienced when using a ruler to measure the height of the .image in this experiment. Suggest an improvement to the apparatus to overcome this
hand or ruler gets in way of light translucent screen (and measure from back) / fix grid to screen Describe one difficulty that might be experienced when measuring the height of the image .h1. Suggest an improvement to the apparatus to reduce this difficulty
hand / ruler in way of image OR some images too small to measure accurately use translucent screen and view from behind OR fix ruler / grid to screen OR mark extremities of image and measure later OR use larger object Ray Trace Experiment
. Suggest a suitable distance apart for the pins for accurate ray tracing
( pin separation should be as large as possible (5 cm min
. Suggest techniques to use in this type of experiment to ensure results are accurate
thin lines / use sharp pencil look at base of pins / keep pins vertical thin pins
. State one precaution that you would take in order to produce an accurate ray trace
view bases of pins ( place pins (as) far apart (as possible ensure pins are vertical sharp pencil / thin lines / thin pins
.Suggest one source of inaccuracy in this experiment, even if it is carried out very carefully
thickness of the light rays difficulty in aligning incident ray with FE difficulty of placing crosses accurately difficult to judge the centre of the ray Suggest one reason why different students, all doing this experiment carefully, may not .obtain identical results
difficult to align pins / place pins accurately / pins (too) thick The measurement of a quantity is reproducible if a similar result is obtained when the measurement is repeated by a different method or under different conditions. Suggest how .the student can adapt this experiment to check if the value of d/l is reproducible
repeat with [angle value] on the other side of the normal OR repeat with optical pins Circuit Experiment Explain one advantage of using a variable resistor for this purpose rather than the procedure .(carried out in (a) and (b
avoids connecting / disconnecting the circuit / can obtain a continuous set of values / easier (to change the current/resistance) / quicker / can obtain more values of resistance / current Name a single device that can be used to control the current in the circuit instead of adding .extra resistors in series
variable resistor
. Suggest one advantage of using a variable resistor to change the current in the circuit
easy to obtain range of values can easily set current to chosen values Briefly explain one advantage of using a variable resistor to determine the resistance of .(resistor U rather than the procedure carried out in (b) and (c
can obtain continuous set of values more straightforward to change current can obtain more values easily Suggest one practical reason why other students might not obtain the same result as this student, even if they do the experiment carefully
uncertain connection point on crocodile clip resistance wire irregular / curved / not uniform / differing thickness along wire Suggest one practical reason why students carrying out this experiment may not obtain the same readings as in Table 3.1. Assume that the procedure has been done carefully
difficult to position crocodile clip accurately inconsistent connection with crocodile clip resistance wire not uniform Suggest one difficulty which explains why different students, doing the experiment carefully with the same equipment, may not obtain identical results
line graph: for continuous values (e.g mass, weight, distance, height) basically numbers ( bar chart: for discontinuous values (e.g color, material compare [independent variable] and [dependent variable] in the table to see if/how they affect each other
For graph label your axis with units if necessary, make sure it takes up 75% of the graph paper, common axis intervals are 5 units and 2 units (can also be 0.5, 0.2, 0.05 ect) make sure it's a thin line
