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PHYSICS · Stage 8 · Chapter 6: Forces, Motion and Pressure

Physics 6.10 Presenting data from springs — Hooke’s Law and Elastic Limit

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Physics 6.10 Presenting data from springs — Hooke's Law and Elastic Limit — Alhussan International Academy — Physics (Stages 7–9) notes: Describe how to record, graph and evaluate a spring-stretching investigation and find the elastic limit.Trampoline springs — A trampoline conta…

  • Categoric variable
  • Line of best fit
  • Anomalous result
  • Reliability
  • Original length
  • Question — How can the elastic limit of a spring be found?

Section 1 of 6Why the elastic limit matters

  • Trampoline springs
    • A trampoline contains many springs that must stay below their elastic limit at the maximum weight on the label.
  • Question
    • How can the elastic limit of a spring be found?

Section 2 of 6Method for stretching a spring

  1. Measure the length of the spring with no weights on it; this is the original length.
  2. Record zero force and zero extension in the table.
  3. Add one 1 N weight and measure the new length with a ruler.
  4. Subtract the original length from the new length to find the extension and write it in the table.
  5. Keep adding weights, measuring each time, until the load reaches 8 N.
  6. Repeat the whole experiment and calculate the mean extension for each weight.
  • Variables
    • Force is the independent variable and extension is the dependent variable.
  • Control
    • Use the same spring and ruler, and read the ruler at eye level.

Section 3 of 6Recording results in a table

  • Headings
    • Each column has a heading with the quantity and its unit, such as Force (N), Length (cm) and Extension (cm).
  • Repeats
    • The table has space for all repeat measurements and the mean.
  • Categoric variable
    • If a variable is a name, such as colour of spring, the results cannot be shown on a line graph.

Section 4 of 6Drawing the graph

  • Variables
    • Both weight and extension are continuous variables, so a line graph is plotted.
  • Axes
    • Weight (force) is on the horizontal axis and mean extension on the vertical axis.
  • Line of best fit
    • It goes through most points and is a smooth line or curve.
    • It starts at the origin (0, 0), because the extension is zero when the force is zero.
    • The line is straight at first, then curves upwards as the load increases.

Section 5 of 6Hooke's law and the elastic limit

  • Hooke's law
    • The extension is directly proportional to the force, giving a straight line through the origin.
  • Elastic limit
    • Beyond this force the graph curves because the extension increases faster than the force.
    • When the force is removed the spring does not return to its original length.
    • If a spring fails to return after a 6 N load, then 6 N is beyond its elastic limit.

Section 6 of 6Anomalous results and reliability

1Anomalous result2 points
= a result that does not fit the pattern.
  • It is probably caused by a measurement error and should be identified on the graph.
  • It should be repeated or checked.
2Reliability3 points
  • Repeating each measurement, for example three times, makes the data more accurate and reliable.
  • A ruler with finer divisions increases precision.
  • Possible errors include a ruler zero that does not match the bottom of the spring and a swinging spring.

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