StudyBrixFree worksheets, study guides and courses

Physics · Grades 9–12

Physics evidence: uncertainty and proportionality

Interpret patterns without turning a short dataset into proof.

Make a worksheet

Learn the idea

Variables

Distinguish the deliberately changed variable, the measured response and controlled conditions.

Proportionality

A straight line through the origin supports direct proportionality over the measured range; other straight lines do not.

Uncertainty

Repeat variation and instrument limits affect confidence. A model fit does not remove measurement uncertainty.

Claims

Use language such as consistent with the model within this range, and identify possible alternative explanations.

Worked examples

Three times are 1.8, 2.0 and 2.2 s. Find their mean.

The sum is 6.0 s, divided by 3.

2 s

Which straight graph supports direct proportionality y = kx?

Direct proportionality requires the zero intercept as well as constant slope.

A straight line through the origin

Check your understanding

  1. A fitted line is F = 4x + 2, with F in N and x in m. Find F at x = 3 m.

  2. Why does an isolated unusual reading need investigation rather than automatic deletion?

  3. A timing device adds the same 0.1 s offset to every reading. What kind of effect is this?

    1. A guaranteed improvement in precision
    2. Systematic offset
    3. Only random scatter

Answers and marking notes

Answers and marking notes
  1. 14 N

    4 × 3 + 2 = 14 N.

  2. It could be an error or a real variation; exclusion needs a documented reason.

    Credit transparent analysis, not selective removal to fit expectations.

  3. Systematic offset

    The error has a consistent direction and size.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.