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Graph Linearization

Instructions for Students & Teachers

  • Graph Linearization trains the skill of turning a curved graph into a straight line, so the slope and intercept reveal a physical quantity.

  • Choose an equation from AP Physics 1 or AP Physics 2, decide what to put on each axis, and apply transforms such as squaring, square roots, or 1/x until the data falls on a line.

  • When the graph is straight, the tool converts the slope (and the y-intercept, when it carries meaning) into the physics: for example, a pendulum's slope becomes a value of g.

  • Explore mode shows every equation with its variables labeled, plus step-by-step hints. Practice mode hides the variables and builds a streak.

  • Note for teachers: This mirrors what students do with lab data and on AP free-response questions: identify the relationship, pick the axes that make it linear, and connect the slope to the physics.

Usage Steps

Course

  • Choose Both, AP Physics 1, or AP Physics 2. The course filter applies to Explore and Practice.

  • Note for teachers: AP Physics 1 classes can stay on the AP Physics 1 filter so students only see equations they have studied.

Equations

  • Pick an equation from the list, or narrow it with the search box or the topic buttons (Kinematics, Forces, Thermodynamics, and so on).

  • A green check marks an equation you solved on your own. A book icon marks one you solved with the Walkthrough.

  • The counter at the top and the numbers on each topic button track your progress.

Graph Setup

  • Choose the x-axis variable first, then the y-axis variable. The y-axis menu only lists variables that pair with your x-axis choice.

  • A greyed-out menu means there is only one choice for that equation.

  • Changing either variable starts a fresh graph and clears your transforms.

  • Mastery tip: Before touching the transforms, predict the shape of the raw graph from the equation. Will it curve up, curve down, or already be straight?

Data and Axis Quantities

  • Some setups ask you to combine measured variables on an axis, like PV or Δx/t. These setups show an x-axis quantity and y-axis quantity menu instead of the variable menus.

  • The ideal gas law has a Data switch: "One of P, V, T held constant" gives the usual graphs, and "P, V and T all change" gives a data set where you must combine quantities.

  • The quantity menus include some combinations that will not work. Choosing the right one is part of the problem.

  • Mastery tip: Rearrange the equation so the quantity you want to find sits where the slope goes. For PV = nRT, writing PV = n(RT) shows that PV vs RT has slope n.

Transforms

  • Each axis has its own transform menu: raw, x², x³, √x, 1/x, 1/x², 1/√x, and ln. Angle variables also offer sin.

  • The graph and data table update as soon as you change a transform.

  • A dashed best-fit line appears when the graph is straight and matches the physics.

  • If a transform can't be applied to some data points (the log of a negative number, or 1 divided by zero), those points disappear from the graph and a note explains why.

  • Mastery tip: Change one axis at a time and watch how the curve bends. It teaches you which transform straightens which shape.

Check

  • Press Check when you think the graph is linear.

  • A correct answer shows the slope, what the slope represents, and the physical quantity it gives. When the y-intercept has meaning (like v₀), it is converted too.

  • Correct rearrangements count. For example, √Δx vs t works as well as Δx vs t², and the tool shows how its slope connects to the usual graph.

  • Some graphs come out straight without revealing anything, such as squaring both axes or taking ln of both. Check explains why those don't count.

  • Reset sets both transforms back to raw.

Walkthrough

  • Walkthrough reveals hints one at a time, from noticing the shape of the graph to reading the slope.

  • An equation solved after opening the Walkthrough gets a book icon in the equation list instead of a green check.

  • Mastery tip: Open only one hint, then try again on your own.

Data Table

  • The table lists the raw data and the values on each axis after your transforms.

  • For combined setups, it shows each measured variable (for example T, V and P) followed by the values you chose to graph.

  • Note for teachers: The table is a good model for how students should set up their own lab data tables, with one column per transformed quantity.

Practice Mode

  • Switch to Practice and press Start practice. Each problem is an unknown equation: the axes are labeled A and B and the variable names are hidden.

  • Choose All or Needs transform to include or skip graphs that are already straight.

  • Find the transforms, press Check, and build a streak. A correct answer reveals the equation and what the slope means.

  • Skip moves to a new problem and resets your streak. The session tally counts first-try solves separately from solves after a wrong Check.

  • Setups that combine quantities (PV vs RT, Δx/t vs t, Δθ/t vs t) appear in Explore only.

  • Mastery tip: In Practice, name the relationship before choosing transforms: inverse, inverse square, square root, or exponential.

Teaching Tips

  • Before a lab: have students find the matching equation in Explore and decide what they will graph before they collect data. They arrive at the lab knowing which columns their data table needs.

  • Introducing linearization: start with Explore and the Walkthrough on a few familiar equations (Δx = ½at², T = 2π√(L/g)), then move to Practice once students can name the relationship without hints.

  • Retrieval practice: short Practice sessions work well as warm-ups. Use the Needs transform filter so every problem requires a decision.

  • Rearrangements: the tool accepts correct rearrangements, such as √Δx vs t or 1/a vs m, and shows how their slope connects to the usual graph. Have students compare two valid graphs for the same equation and explain why both slopes give the same answer. Rearranging an equation into a linear form also shows up on AP free-response questions.

  • Graphs with an intercept: Δx = v₀t + ½at² is straight as Δx/t vs t, with slope ½a and y-intercept v₀. Δx vs t² is only straight when v₀ is zero. It is a good challenge for students who think every graph through the origin is the goal. Its rotational match, Δθ = ω₀t + ½αt², works the same way.

  • Combined quantities: the ideal gas data set where P, V and T all change shows why holding variables constant matters in a lab, and how combining quantities (PV vs RT) recovers the number of moles when nothing is held constant.

  • Exponential relationships: radioactive decay needs ln to straighten its graph. Plotting ln N vs t gives the decay constant from the slope and the half-life from t½ = ln 2/λ.

  • Discussion question: after a correct Check, ask "What would change on this graph if the constant in the slope doubled?" It connects the graph back to the physics rather than to the procedure.

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