Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Exemplar for Internal Assessment Resource
Physics Level 1
This exemplar supports assessment against:
Achievement Standard 90935
Carry out a practical physics investigation that leads to a linear
mathematical relationship, with direction
Student and grade boundary specific exemplar
The material has been gathered from student material specific to an A or B assessment
resource.
Date version published by
Ministry of Education
© Crown 2011
December 2011
To support internal assessment from 2012
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: Low Excellence
1.
At the Excellence level the students are required to carry out a comprehensive practical
physics investigation, with direction, that leads to a linear mathematical relationship.
Carrying out a comprehensive practical physics investigation involves writing a
discussion that validates the conclusion.
The discussion may include as appropriate:
 a justification for the accuracy-improving techniques used, a reason that there is
a limit to either end of the value chosen for the independent variable
 a justification why a variable needs to be controlled
 a description of any difficulties encountered when making measurements and
how these difficulties were overcome
 a link between investigation findings and applicable physics ideas
 a description of any unexpected outcomes of the processing of the results and
a suggestion of how these outcomes could have been caused and/or the effect
they had on the validity of the conclusion.
The report mentions the fact that the intercept on the graph does not reflect the length
of the spring when no mass has been added, however what has caused this is not
discussed and the effect on the validity of the conclusion is not included. The control
variable statement about why the spring needs to be controlled has been justified but
not quite to the excellence level.
A link has been made to the theoretical equation of Hooke’s Law and how by
rearranging the equation found from the graph, the gradient links to the spring
constant. This has also been linked back to the graph for the original experiment. This
comment, in addition to the two weaker comments, means the discussion is just at the
excellence level.
To achieve the standard at the Excellence level more securely the student could
include the following:
 a justification for the accuracy-improving techniques used
 a reason that there is a limit to either end of the value chosen for the
independent variable
 a full justification why a variable needs to be controlled
 a description of any difficulties encountered when making measurements and
how these difficulties were overcome
 a suggestion of how these unexpected outcomes could have been caused
and/or the effect they had on the validity of the conclusion.
© Crown 2011
Student 1: Low Excellence
Practical Title:
Name:
Planning Template
Aim:
To find the mathematical relationship between the length of the stretched spring and the mass
that is causing it to stretch.
Independent and Dependent variables
Which variable will be changed? (This is the independent variable).
The mass (m).
How will the independent variable be changed?
Adding 20g masses to the mass holder on the spring each time
Give a suitable range of values for this variable.
20g, 40g, 60g, 80g and 100g.
Which variable will be measured or observed as the output of your investigation? (This is the dependent
variable)
The length of the stretched spring.
How will the dependent variable be measured or observed?
Using a ruler to measure the length in cms.
Other variables that need to be controlled to make your results more accurate
Variable
How this variable will be controlled
Same spring
The same spring will be used throughout the experiment as
different springs can stretch differently.
Same ruler
Use the same ruler and measure in the same place from the top of
the spring to the bottom of the spring each time.
Same masses
Use the same masses as there maybe some variation in the actual
weight of the slotted masses.
How will you ensure that your results are reliable?
By repeating the experiment at least 3 times and averaging the results.
Looking at the ruler at eye level to reduce parallax error.
My Method and the data:
o
Hang a spring from a clamp and stand and measure the length of the spring before the
mass is added using the
ruler. Measure the length
from the top of the spring to
the bottom of the spring.
Mass in
grams
1
0
20
40
60
80
100
20
23
32
40
51
60
Length in cms
2
3
20
24
35
41
50
58
Average
20
22
33
39
50
59
20
23
33.3
40
50.3
59
o
Hang the mass holder from
the bottom of the spring and
wait until the spring is
steady. Record the length.
The mass holder is 20g.
o
The ruler should be as close
as possible to the spring and should be viewed at eye level to minimise the parallax error.
o
Repeat the last two steps adding 20g each time until 100g.
o
Repeat the investigation at least 3 times in enough time and average the results.
Describing the Relationship
From the graph it can be seen that as the amount of mass attatched to the spring increases
the distance the spring stretches in increased. The gradient of the graph = 0.4051 and the
equation is y = 0.4051  x or length = 0.4051  mass. The intercept is around 17.3cm, in
the experiment the length before th mass was added was 20cm so there is an error which
makes the line of best fit too low as it crosses the axis.
Conclusion
The equation which shows the strength of a spring is Hooke’s law which states that F=kx. Where F is the restoring force, k is the spring constant and x is the extension. I have
measured mass and length, these need to be converted to the units of newtons and meters.
The gradient is the spring constant and is 2.24, this is the inverse of the gradient of the original
graph which can also give the spring constant. This will be different for a different spring.
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: High Merit
2.
At the Merit level the students are required to carry out an in-depth practical physics
investigation, with direction, that leads to a linear mathematical relationship.
Carrying out an in-depth practical physics investigation involves:
 controlling the variable(s) that could have a significant effect on the results
 using technique(s) that increase the accuracy of the measured values of the
dependent (and independent, if appropriate) variable
 drawing a linear graph, valid for the data,
 writing a conclusion that states the equation of the relationship.
The control variables have been stated and the accuracy-improving technique of
repeating and averaging has been used. A linear graph which reflects the collected
data has been drawn. The gradient for the line of best fit has been calculated and the
equation of the mathematical relationship has been given. The use of the accuracy
techniques have been described but it has not been explained why the techniques
have increased the accuracy. The spring has to be controlled and the same spring
being used has been mentioned, however the different rates of stretching has not been
investigated in the experiment. The explanation for the choice of values for
independent variable is reasonable but not detailed enough for excellence. The
discussion of the difficulty is not a valid issue.
To achieve the standard at the Excellence level the student could include the following:
 a justification for the accuracy-improving techniques used
 a reason that there is a limit to either end of the value chosen for the
independent variable
 a justification for why a variable needs to be controlled
 a description of any difficulties encountered when making measurements and
how these difficulties were overcome
 a link between investigation findings and applicable physics ideas
 a description of any unexpected outcomes of the processing of the results and
a suggestion of how these outcomes could have been caused and/or the effect
they had on the validity of the conclusion.
© Crown 2011
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: Low Merit
3.
The control variables have been stated and the accuracy improving technique of
repeating and averaging has been used. The linear graph has been shown and
labelled, however the graph size is too small to accurately reflect the data. The line of
best fit has been applied, however it has been constructed by joining the first and last
lines which means most points lie below the line. The gradient has been calculated.
The mathematical equation has been stated, and although it has been stated in terms
of y and x, the variables have been described in the conclusion.
To achieve the standard at the Merit level more securely the student could draw a
graph of the data of an appropriate size to reflect the data accurately.
© Crown 2011
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: High Achieved
4.
At the achieved level the students are required to carry out a practical physics
investigation, with direction, that leads to a linear mathematical relationship.
Carrying out a practical physics investigation involves:
 developing a method for collecting the data
 collecting primary data, with units, relevant to the purpose, based on the
manipulation of the independent variable over a reasonable range and number
of values
 drawing a graph, based on the data
 writing a conclusion that links the processed data to the identified trend on the
graph.
The control variables have been stated, however the use of the same spring, which
would have the biggest effect, has not been included. The accuracy technique of
repeating and averaging has been used. The linear graph of the data has been shown.
The gradient has been calculated but the value and equation are not consistent with
the line of best fit.
To achieve the standard at the Merit level the student could include:
 the control variable that would have the most significant effect on the results
 an equation that accurately reflects the relationship.
© Crown 2011
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: Low Achieved
5.
The method has been developed to collect the data. Data relevant to the experiment
with the appropriate units have been recorded. A graph based on the data has been
drawn. The initial conclusion does not reflect the identified trend on the graph as it does
not show a 1.5cm increase for every 40g, however the last statement given about the
relationship shows a marginal understanding of the trend.
To achieve the standard more securely the student could write a conclusion that clearly
links the processed data to the identified trend on the graph.
© Crown 2011
Exemplar for internal assessment resource Physics for Achievement Standard 90935A
Grade Boundary: High Not Achieved
6.
A basic method has been developed to complete the experiment. The data has been
collected with the appropriate units given in the data table. A reasonable range
appears to have been used for the independent variable, however the first two
measurements are not near the line of best fit, which may indicate the spring was
permanently stretched. The value of the spring’s initial length compared to the
subsequent values for the spring’s extension, do not seem to be consistent. The graph
shows an inconsistent value for the initial length to that recoded in the results table. A
linear graph has been drawn for the data. The conclusion links to the data recorded
and the graph.
To achieve the standard the student could include:
 a collection of the primary data that is reasonable for the experiment being
attempted
 a value for the initial spring length recorded that is reflected by the graph.
© Crown 2011