Define mean (in the context of repeat readings).

The mean is calculated by dividing the sum of the repeat readings by the number of readings taken. Any anomalous readings are excluded before calculating it.

Why should anomalous readings be excluded when calculating a mean?

Because they are not genuine readings, and including them would distort the mean away from the true value.

The mean should have the .......... number of significant figures as the readings used to calculate it.

The mean should have the same number of significant figures as the readings used to calculate it.

In the Hooke's law experiment, how is the extension of a spring calculated?

Extension is found by subtracting the initial length from the final length of the spring — it is not measured directly.

Why is it useful to include a column for the 'log' of a measured quantity in a data table?

So the calculated log values are ready to use for plotting a log-log graph , without extra working during the practical.

Define the axis labelling convention used for physics graphs.

Each axis is labelled with the quantity's name (or symbol), a forward slash, then its unit , e.g. F / N.

What fraction of the graph grid should a plotted graph occupy, in both directions?

At least half of the graph grid in both the x and y directions.

Which variable is plotted on the x-axis, and which on the y-axis?

The independent variable goes on the x-axis and the dependent variable goes on the y-axis.

Points must be plotted to a precision of within .......... of a small square.

Points must be plotted to a precision of within half a small square.

True or False? A line of best fit should always be forced through the origin.

False. Not all lines pass through the origin, and they should not be forced to — the line must reflect the actual trend of the data .

What is the key difference between the command words 'sketch' and 'plot' when drawing a graph?

A sketch needs labelled axes but no scale; a plotted graph requires a suitable scale and points marked accurately from data, with a line of best fit drawn through them.

Define SI base units .

The seven fundamental units (e.g. kg, m, s, A) from which the units of every other physical quantity are derived.

The Pascal (Pa), the unit of pressure, is defined as force divided by .......... .

The Pascal (Pa), the unit of pressure, is defined as force divided by area .

True or False? Every physical quantity in physics has a unit.

False. Some quantities are dimensionless and have no unit, such as refractive index or the number of particles .

Define a directly proportional relationship.

As one variable increases, the other increases at the same rate ; represented by a straight line through the origin.

Define an inversely proportional relationship.

As one variable increases, the other decreases at the same rate; represented by a curve with a decreasing gradient.

A straight horizontal line on a graph shows that the dependent variable is .......... as the independent variable changes.

A straight horizontal line on a graph shows that the dependent variable is constant as the independent variable changes.

True or False? If two variables are directly proportional, doubling one will always double the other, even if a third variable in the equation also changes.

False. The relationship only holds if all other variables remain constant — if another variable changes too, the direct proportionality breaks down.

What shape of graph indicates an inversely proportional relationship?

A curve with a continuously decreasing gradient .

Define an inverse square law relationship.

y is inversely proportional to x 2 ; if x doubles, y decreases by a factor of four .

What must be true of the other variables in an equation before two variables can be called directly or inversely proportional?

All the other variables in the equation must remain constant .

The gradient triangle drawn on a graph should be as .......... as possible.

The gradient triangle drawn on a graph should be as large as possible.

What determines the units of a graph's gradient?

The ratio of the units of the y -variable to the units of the x -variable.

True or False? When calculating a gradient, it is acceptable to use two individual data points that don't lie exactly on the line of best fit.

False. The gradient triangle should use points on the line of best fit , not raw data points that lie away from it.

What is a fiducial marker ?

A fixed reference point used to improve timing accuracy, e.g. sighting a pendulum as it passes a marker at its lowest point (highest speed).

Define parallax error .

An error caused by reading a scale at an angle rather than perpendicular to it (at eye level).

Why should pendulum timings be taken as it passes the fiducial marker at the bottom of its swing, rather than at the top?

The pendulum moves fastest at the bottom, reducing the timing (reaction-time) error compared with the slower motion at the top.

How can the effect of random errors on a result be reduced?

By taking repeat readings and using the average (mean) of them.

A common way to reduce unwanted heating effects in a circuit is to .......... the power supply between readings.

A common way to reduce unwanted heating effects in a circuit is to turn off the power supply between readings.

True or False? Taking more repeat readings will eliminate a systematic error in an experiment.

False. Repeats only reduce the effect of random error ; a systematic error (e.g. a zero error) affects every reading equally and must instead be corrected, such as by checking for zero error.

What is a data logger ?

A data logger is an electronic device that automatically monitors and records environmental parameters (e.g. temperature, pressure, voltage or current) over time, using sensors and a computer chip to store the data.

How can a camera be used to determine a property such as velocity in an experiment that happens too quickly to read a scale directly?

A photo burst is taken as the experiment happens, so the scale can be read from the photos afterwards. If the time each photo was taken (or the frame rate) is known, properties such as velocity can then be calculated.

Give three benefits of using data loggers instead of manual data collection.

Higher degree of accuracy Reduction in human error, e.g. reaction time Readings taken over very long or very short time periods Reduced safety risk in extreme conditions

Define reproducibility .

Reproducibility is the ability of an experimental method to be repeated by other scientists, or applied to other systems, and still produce comparable results.

How can the method for measuring the resistivity of a constantan wire be shown to be reproducible?

By using the same method to measure the resistivity of a different material, such as copper or aluminium, and obtaining an accurate value. This shows the method itself is reproducible, not just the result for one material.

Using digital methods of data collection, such as data loggers, reduces uncertainties that result from .......... , such as reaction time.

Using digital methods of data collection, such as data loggers, reduces uncertainties that result from human error , such as reaction time.

True or False? Computer modelling can be used to speed up time in order to predict the future outcome of an experiment.

True. Computer modelling processes data collected from an experiment (often via a data logger) into software, and one of its benefits is that time can be sped up to predict future outcomes.

Define absolute uncertainty .

Absolute uncertainty is uncertainty given as a fixed quantity, expressed in the same units as the measurement.

Define fractional uncertainty .

Fractional uncertainty is uncertainty given as a fraction of the measurement.

What is the uncertainty in a single reading taken from an analogue scale?

± half the smallest division on the scale.

What is the uncertainty in a digital reading?

± the last significant digit shown, unless otherwise quoted.

How do you combine uncertainties when multiplying or dividing two measured quantities?

Add the percentage (or fractional) uncertainties of the two quantities.

How do you find the uncertainty in a quantity that has been raised to a power?

Multiply the percentage uncertainty of the quantity by the power.

When adding or subtracting data, you .......... the absolute uncertainties of each value.

When adding or subtracting data, you add the absolute uncertainties of each value.

True or False? The uncertainty in a constant, such as π , is taken to be zero.

True. Constants such as π are exact values, so they carry no uncertainty when used in calculations.

How is the absolute uncertainty of a single analogue reading found from the instrument's resolution?

It is half the resolution (smallest division) of the instrument.

How is the uncertainty in the mean of a set of repeat readings calculated?

Half the range of the readings: ± ½ × (highest value − lowest value).

The uncertainty in a set of repeat readings is taken as .......... the range of the values.

The uncertainty in a set of repeat readings is taken as half the range of the values.

True or False? Percentage uncertainty is expressed with the same units as the measured quantity.

False. Percentage uncertainty has no units — it is expressed only as a percentage (%).

International A Level (IAL)PhysicsEdexcelFlashcards3. Practical Skills in Physics IPractical Skills I: Processing Results

Practical Skills I: Processing Results (Edexcel International A Level (IAL) Physics): Flashcards

Exam code: YPH11

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FrontCalculations using Experimental Data
Define mean (in the context of repeat readings).

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Cards in this collection (58)

Define mean (in the context of repeat readings).
The mean is calculated by dividing the sum of the repeat readings by the number of readings taken. Any anomalous readings are excluded before calculating it.
Why should anomalous readings be excluded when calculating a mean?
Because they are not genuine readings, and including them would distort the mean away from the true value.
The mean should have the .......... number of significant figures as the readings used to calculate it.
The mean should have the same number of significant figures as the readings used to calculate it.
In the Hooke's law experiment, how is the extension of a spring calculated?
Extension is found by subtracting the initial length from the final length of the spring — it is not measured directly.
True or False?
The area of a wire can be measured directly using a micrometer.
False.
A micrometer measures the wire's radius; the area is then calculated using $A = π r^{2}$ from that measurement.
Why is it useful to include a column for the 'log' of a measured quantity in a data table?
So the calculated log values are ready to use for plotting a log-log graph, without extra working during the practical.
Define the axis labelling convention used for physics graphs.
Each axis is labelled with the quantity's name (or symbol), a forward slash, then its unit, e.g. F / N.
What fraction of the graph grid should a plotted graph occupy, in both directions?
At least half of the graph grid in both the x and y directions.
Which variable is plotted on the x-axis, and which on the y-axis?
The independent variable goes on the x-axis and the dependent variable goes on the y-axis.
Points must be plotted to a precision of within .......... of a small square.
Points must be plotted to a precision of within half a small square.
What is the minimum number of points that should be plotted on a graph?
At least six points.
True or False?
A line of best fit should always be forced through the origin.
False.
Not all lines pass through the origin, and they should not be forced to — the line must reflect the actual trend of the data.
What is the key difference between the command words 'sketch' and 'plot' when drawing a graph?
A sketch needs labelled axes but no scale; a plotted graph requires a suitable scale and points marked accurately from data, with a line of best fit drawn through them.
Define SI base units.
The seven fundamental units (e.g. kg, m, s, A) from which the units of every other physical quantity are derived.
Derive the SI base units of the Newton (N) from $F = m a$ .
$N = {kg m s}^{- 2}$
Derive the SI base units of the Joule (J) from $E_{k} = \frac{1}{2} m v^{2}$ .
$J = {kg m}^{2} s^{- 2}$
The Pascal (Pa), the unit of pressure, is defined as force divided by ...........
The Pascal (Pa), the unit of pressure, is defined as force divided by area.
What is 1 cm³ equivalent to, in millilitres?
1 cm³ = 1 ml (millilitre).
True or False?
Every physical quantity in physics has a unit.
False.
Some quantities are dimensionless and have no unit, such as refractive index or the number of particles.
Define a directly proportional relationship.
As one variable increases, the other increases at the same rate; represented by a straight line through the origin.
Define an inversely proportional relationship.
As one variable increases, the other decreases at the same rate; represented by a curve with a decreasing gradient.
In the ideal gas equation $P V = n R T$ , what is the relationship between n and T at constant P and V?
n is inversely proportional to T.
A straight horizontal line on a graph shows that the dependent variable is .......... as the independent variable changes.
A straight horizontal line on a graph shows that the dependent variable is constant as the independent variable changes.
True or False?
If two variables are directly proportional, doubling one will always double the other, even if a third variable in the equation also changes.
False.
The relationship only holds if all other variables remain constant — if another variable changes too, the direct proportionality breaks down.
What shape of graph indicates an inversely proportional relationship?
A curve with a continuously decreasing gradient.
Define an inverse square law relationship.
y is inversely proportional to x²; if x doubles, y decreases by a factor of four.
In $F = \frac{L}{4 π d^{2}}$ , how does F change if the distance d is tripled?
F decreases by a factor of 3² = 9.
What must be true of the other variables in an equation before two variables can be called directly or inversely proportional?
All the other variables in the equation must remain constant.
The gradient triangle drawn on a graph should be as .......... as possible.
The gradient triangle drawn on a graph should be as large as possible.
What determines the units of a graph's gradient?
The ratio of the units of the y-variable to the units of the x-variable.
True or False?
When calculating a gradient, it is acceptable to use two individual data points that don't lie exactly on the line of best fit.
False.
The gradient triangle should use points on the line of best fit, not raw data points that lie away from it.
What is a fiducial marker?
A fixed reference point used to improve timing accuracy, e.g. sighting a pendulum as it passes a marker at its lowest point (highest speed).
Define parallax error.
An error caused by reading a scale at an angle rather than perpendicular to it (at eye level).
Why should pendulum timings be taken as it passes the fiducial marker at the bottom of its swing, rather than at the top?
The pendulum moves fastest at the bottom, reducing the timing (reaction-time) error compared with the slower motion at the top.
How can the effect of random errors on a result be reduced?
By taking repeat readings and using the average (mean) of them.
A common way to reduce unwanted heating effects in a circuit is to .......... the power supply between readings.
A common way to reduce unwanted heating effects in a circuit is to turn off the power supply between readings.
True or False?
Taking more repeat readings will eliminate a systematic error in an experiment.
False.
Repeats only reduce the effect of random error; a systematic error (e.g. a zero error) affects every reading equally and must instead be corrected, such as by checking for zero error.
What is a data logger?
A data logger is an electronic device that automatically monitors and records environmental parameters (e.g. temperature, pressure, voltage or current) over time, using sensors and a computer chip to store the data.
How can a camera be used to determine a property such as velocity in an experiment that happens too quickly to read a scale directly?
A photo burst is taken as the experiment happens, so the scale can be read from the photos afterwards. If the time each photo was taken (or the frame rate) is known, properties such as velocity can then be calculated.
Give three benefits of using data loggers instead of manual data collection.
- Higher degree of accuracy
- Reduction in human error, e.g. reaction time
- Readings taken over very long or very short time periods
- Reduced safety risk in extreme conditions
Define reproducibility.
Reproducibility is the ability of an experimental method to be repeated by other scientists, or applied to other systems, and still produce comparable results.
How can the method for measuring the resistivity of a constantan wire be shown to be reproducible?
By using the same method to measure the resistivity of a different material, such as copper or aluminium, and obtaining an accurate value. This shows the method itself is reproducible, not just the result for one material.
Using digital methods of data collection, such as data loggers, reduces uncertainties that result from .........., such as reaction time.
Using digital methods of data collection, such as data loggers, reduces uncertainties that result from human error, such as reaction time.
True or False?
Computer modelling can be used to speed up time in order to predict the future outcome of an experiment.
True.
Computer modelling processes data collected from an experiment (often via a data logger) into software, and one of its benefits is that time can be sped up to predict future outcomes.
Define absolute uncertainty.
Absolute uncertainty is uncertainty given as a fixed quantity, expressed in the same units as the measurement.
Define fractional uncertainty.
Fractional uncertainty is uncertainty given as a fraction of the measurement.
What is the uncertainty in a single reading taken from an analogue scale?
± half the smallest division on the scale.
What is the uncertainty in a digital reading?
± the last significant digit shown, unless otherwise quoted.
How do you combine uncertainties when multiplying or dividing two measured quantities?
Add the percentage (or fractional) uncertainties of the two quantities.
How do you find the uncertainty in a quantity that has been raised to a power?
Multiply the percentage uncertainty of the quantity by the power.
When adding or subtracting data, you .......... the absolute uncertainties of each value.
When adding or subtracting data, you add the absolute uncertainties of each value.
True or False?
The uncertainty in a constant, such as π, is taken to be zero.
True.
Constants such as π are exact values, so they carry no uncertainty when used in calculations.
Define percentage uncertainty.
$Percentage uncertainty = \frac{uncertainty}{measured value} \times 100 %$
How is the absolute uncertainty of a single analogue reading found from the instrument's resolution?
It is half the resolution (smallest division) of the instrument.
A student measures a potential difference on an analogue voltmeter of resolution 0.2 V as 15 V. Calculate the percentage uncertainty in this reading.
$absolute uncertainty = \frac{0.2}{2} = 0.1 V$
$percentage uncertainty = \frac{0.1}{15} \times 100 % = 0.67 %$
How is the uncertainty in the mean of a set of repeat readings calculated?
Half the range of the readings: ± ½ × (highest value − lowest value).
The uncertainty in a set of repeat readings is taken as .......... the range of the values.
The uncertainty in a set of repeat readings is taken as half the range of the values.
True or False?
Percentage uncertainty is expressed with the same units as the measured quantity.
False.
Percentage uncertainty has no units — it is expressed only as a percentage (%).

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