3.B Making Claims from Theory & 3.C Justifying Claims

How to approach making and justifying claims

Any time you attempt to make a claim about a physical situation you should use a the ABCD method to ensure your claim is correct and that you justify it in a way others will understand. Go through these steps mentally for a multiple-choice question and document them clearly on an open-ended response. 

A. Answer the question (these are the claims in Science Skill 3.B)

• Do the BCD first so you know what answer to choose. Very often choosing the answer first makes you force your way through an incorrect justification. Then you can either add the answer to the beginning of your argument or it at the end. 

• Box the simplest, most direct form of your answer. 

• If the FRQ has you place a checkmark next to your answer that is sufficient - and don't forget to do that!

• examples: "the momentum of A is greater," "No," or "the mechanical energy decreased."

B. Basic Physics

• Basic Physics can include facts, principles, definitions, relationships, and, if not prohibited, equations that should be part of any Physics notebook because they are statements that are true about the universe in general and we are bringing up because we will apply them to this situation. 

• Select what physics to bring up based on what will connect the answer to the terms and data in the question prompt. 

• If you don't remember the name of the law, that is OK. Just describe the important part of it. 

• examples: "average speed = distance divided by time," "area under a velocity (time) graph is equal to displacement," "total linear momentum in an isolated system remains constant," or "Static friction adopts the value required to prevent an object from sliding on a surface."

C. Contextual Evidence

• Contextual evidence comes from the question information given about the scenario.  It should be something you could point out with just a highlighter or by pointing, without any additional Physics knowledge. It can be . . .

  • details from the text of the prompt
    examples: the prompt states the acceleration is uniform;  the prompt states v2 = 2v 

  • data from the a data table
    examples: the data table shows the initial velocity was 15 m/s and it took 3 seconds to reach v=0 m/s; the data table shows the velocity in case A decreased more each second than in case B; 

  • trends or values from a graph**
    examples: the graph shows that v = 6 m/s at t=3 s; the slope of the graph for A is greater than for B
    *Note: contextual evidence is specific to what is shown on the graph (say "the velocity increases" instead of "the graph goes up") and does not extend beyond what is shown on the graph (say "the slope of the position (time) graph is constant and positive," instead of "the graph shows the velocity is constant and positive," which is part of the next step - drawing it together).

  • features from a diagram
    examples: the diagram shows the velocity and acceleration are in opposite directions; the diagram shows the total distance traveled is greater in case A than in B 

  • etc. 

• Select what evidence to bring up by thinking about the question is asking and what physics principles can apply to the situation. 

D. Draw it Together (these are the justifications in Science Skill 3.C)

• Connects the basic physics and contextual evidence to the answer. 

• Sometimes this can involves connecting several elements of basic physics with several bits of contextual evidence. 

• For calculations this can be the manipulation and substitution steps.  

• This step might not be needed for simple questions where the physics and context lead naturally and easily to the correct answer.

See examples below.