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Hooke's Law

Grades 9-12 Performance Task
Contributed by: New York State Education Department (NYSED)
Developed through University of Buffalo and NORC (1991)

Task-Specific Scoring Criteria for Physics Task #1: Hooke's Law


1. Statement of hypothesis  
- Effect linked to variables Stretching of a spring when a force is pulling it
- Directionality of effect *
- Expected effect/change The greater the applied force, the greater the stretch
- Independent variable Stretching (elongation or displacement) (S)
- Dependent variable Force (weight, pull)
2. Procedures for investigation  
- Detailed procedure/experimentally feasible Find k which can be derived from the F vs S graph (either calculate slope or extrapolate to the point of the question). More than five data points to be collected.
- Sequence to plan Record zero position (reference point). Move in steps with increasing mass. Read displacement on meter stick.
- General strategy Increase applied force, observe new displacement. Record both observations.
- Safety procedures *
- Use of equipment/diagram Hook up spring. Secure meter stick alongside.
3. Plan for recording and organizing observations/data  
- Space for manipulation of data or qualitative description Construct a data table with m, F and X columns. State explicitly: F = m * g
- Matched to plan Plan for observations and data matched procedure in 2 above.
- Organized sequentially Organized so that recording follows data as generated.
- Labelled fully (units included) Identify units for m (g or kg), conversion to F (N). Units for X in cm.
- Variables identified Force is mass * g and displacement.


* These elements were not scored in this task; a "holistic" scoring approach was utilized so that the other four elements had a total value of 5 points.


4. Quality of observations/data  
- Consistent data Increase m --> observe increase in X
- Accurate measurements/ observations Measurements of m and X within g and mm accuracy of instruments used.
- Completed data table Elongation data for all masses recorded in table and force calculated for all masses (at least five).
- Correct units m (kg), F (N), X (m)
- Qualitative description *
5. Graph  
- Curve is appropriate to data trend Straight line (best fit)
- Points plotted accurately Points correspond to data values in the table
- Appropriate scale Scales can accommodate range of Force vs Stretch
- Axes labelled with variables Force in newtons, stretch in meters.
- Variables placed on correct axes Force on x axis; Stretch (X) on y axis.
6. Calculations  
- Calculated accurately Calculated accurately with appropriate use of significant figures.
- Substituted correctly into relationship Data for graph inserted into ratio: delta F/ delta S
- Relationship stated or implied Slope is the ratio of force over stretch
- Units used correctly Force (N), Stretch (m), slope (N/m)
- Use all data available For slope calculation, the chosen points should be ON the straight line, far from each other.
7. Conclusion  
- Consistent with scientific principle Correctly and clearly matches scientific principle
- Sources of error *
- Consistent with data Conclusion/answer to question is consistent with student's experimental data.
- Relationship among variables stated **
- Variables stated in conclusion Force and displacement (or their symbols) are used in answer.


* These elements were not scored in this task; a "holistic" scoring approach was utilized so that the other four elements had a total value of 5 points.

** Problem statement specified stretching characteristics of spring to be checked.


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