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### Commentary

## Low Excellence

91168 Exemplar Low Excellence (PDF | 46 KB)### Commentary

For Excellence, the student needs to carry out a comprehensive practical physics investigation that leads to a non-linear mathematical relationship.

This involves writing a discussion that addresses critical issues. Each discussion point could relate to:

- a justification for an action that was taken
- an explanation for how a difficulty was dealt with
- an explanation for an unexpected result
- a link between the experimental result and physics ideas.

See Explanatory Note 2 (EN2) for more detail.

This student has comprehensively investigated the non-linear relationship between the distance that a marble travels down a ramp and the time it takes to do so.

This student has attempted to justify the accuracy improving techniques that have been used (1) (2), and has made two attempts to explain the lower than expected value for the acceleration of the marble (4) (5).

For a more secure Excellence, the student could make their investigation more comprehensive by:

- stating why there was likely to be a parallax error in the distance measurement, relating the required positioning of the zero mark on the ruler to the starting position of the marble, and explaining why repeating and averaging reduces the error in the timing measurements
- calculating the value of the friction force, and make a judgement on how likely it is that the lower than expected value for the acceleration could be attributed to friction only.

## High Merit

91168 Exemplar High Merit (PDF | 180 KB)### Commentary

For Merit, the student needs to carry out an in-depth practical physics investigation that leads to a non-linear mathematical relationship.

This involves:

- controlling significant variable(s)
- using appropriate accuracy improving techniques
- stating the mathematical relationship.

See Explanatory Note 2 (EN2) for more detail.

This student has investigated, in depth, the non-linear relationship between the distance that a marble travels down a ramp and the time it takes to do so.

This student has gathered and processed data appropriately and has stated the mathematical relationship. An attempt has been made to justify the accuracy improving techniques that have been used (1) and to explain the control of a significant variable (2). The student has attempted to explain the unexpected difference between the theory and experimental results (3) (4).

To reach Excellence, the student could make their investigation comprehensive by:

- explaining why repeating and averaging makes reaction time error less apparent.
- giving a reason, that relates specifically to this experimental set up, for the need to control the angle of the slope
- giving an accurate explanation for why friction affects the acceleration of the marble down the ramp.

## Low Merit

91168 Exemplar Low Merit (PDF | 102 KB)### Commentary

For Merit, the student needs to carry out an in-depth practical physics investigation that leads to a non-linear mathematical relationship.

This involves:

- controlling significant variable(s)
- using appropriate accuracy improving techniques
- stating the mathematical relationship.

See Explanatory Note 2 (EN2) for more detail.

This student has investigated, in depth, the non-linear relationship between the distance that a marble travels down a ramp and the time it takes to do so.

This student has used appropriate accuracy improving techniques (1) (3). The student has attempted to describe the control of significant variables (2) and has attempted to identify the mathematical relationship (4).

For a more secure Merit, the student could make their investigation more in-depth by:

- making it clear that the the variables described needed to be kept constant in order to control them
- including details of how the gradient was calculated, in order to confirm that the correct technique was used.

## High Achieved

91168 Exemplar High Achieved (PDF | 120 KB)### Commentary

For Achieved, the student needs to carry out a practical physics investigation that leads to a non-linear mathematical relationship.

This involves:

- collecting relevant data over a reasonable range and number of values
- drawing a graph that shows the required relationship
- writing a conclusion which describes the type of mathematical relationship.

See Explanatory Note 2 (EN2) for more detail.

This student has investigated, in depth, the non-linear relationship between the distance that a marble travels down a ramp and the time it takes to do so.

This student has collected six sets of data over an appropriate range of values (2). An appropriate non-linear graph has been drawn (3) and the student has correctly stated the type of relationship (4).

The student has used increased accuracy by repeating and averaging the time measurements (2) and has reduced parallax error when measuring distances (6). The student has made an attempt to identify a variable that needs to be controlled (1) and to construct the correct mathematical equation (5).

To reach Merit, the student could:

- state that the appropriate angle identified for the ramp should be controlled by keeping it constant
- draw a correct linear graph from which to construct the equation, by correctly labelling the transformed variable axis
- using the transformed variable in the equation of the relationship.

## Low Achieved

91168 Exemplar Low Achieved (PDF | 121 KB)### Commentary

For Achieved, the student needs to carry out a practical physics investigation that leads to a non-linear mathematical relationship.

This involves:

- collecting relevant data over a reasonable range and number of values
- drawing a graph that shows the required relationship
- writing a conclusion which describes the type of mathematical relationship.

See Explanatory Note 2 (EN2) for more detail.

This student has collected six sets of data over an appropriate range of values (1). An attempt has been made to process the data so that an appropriate non-linear graph can be drawn (2). The student has correctly stated the type of relationship (3).

For a more secure Achieved, the student could:

- use more appropriate rounding when processing the data
- plot all of the data points correctly
- draw a graph line that is a better fit to the plotted points.

## High Not Achieved

91168 Exemplar High Not Achieved (PDF | 106 KB)### Commentary

For Achieved, the student needs to carry out a practical physics investigation that leads to a non-linear mathematical relationship.

This involves:

- collecting relevant data over a reasonable range and number of values
- drawing a graph that shows the required relationship
- writing a conclusion which describes the type of mathematical relationship.

See Explanatory Note 2 (EN2) for more detail.

The student has collected data over an appropriate range of values (1) and has attempted to draw an appropriate graph to show the relationship (2).

To reach Achieved, the student could:

- plot all of the points on the graph accurately
- describe the type of mathematical relationship that exists between the variables.

This annotated exemplar is intended for teacher use only. Annotated exemplars are extracts of student evidence, with commentary, that explain key parts of a standard. These help teachers make assessment judgements at the grade boundaries.

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