Diagnostic · Forces, FBDs, N3
Newton's Laws Diagnostic
Maps the force misconceptions behind correct-looking answers, such as impetus, N = mg and third-law cancellation. It shows, module by module, which ones your class's answers point to.
IB DP · AP · A-Level · GCSE / IGCSE
6 modules
Forms
14 / module
Questions
~15 / module
Minutes
29 clusters
Bands
FundaFirst HS diagnostics have run in classrooms at 10 schools · 9 countries · 3 continents
The wrong ideas come from physics education research, which has recorded them since the 1970s: Viennot, Trowbridge & McDermott, Arons, Hestenes, Maloney. The physics comes from Arons, Knight, Moore, and Chabay & Sherwood.
“I carried out a pilot test of the Physics Misconceptions Diagnostics with my Grade 11 (lower 6th) International Baccalaureate classes, as part of their revision for end of year exams. The tests covered Motion Foundations, Forces and Free-Body Diagrams - topics that are fundamental to the IB course as well as A’ level courses.
The tests were all set up by FundaFirst - all I had to do was point the students to web links. The students found the questions easy to access and to carry out. The information that came back from FundaFirst was incredibly useful, identifying areas where the class and/or individuals were weaker. These areas would have been much harder to identify without the tests. FundaFirst then provided concrete examples of how to address the misconceptions, with work sheets targeting these areas.
I will not hesitate to use FundaFirst’s diagnostic testing with future cohorts!”
Dr Tim Short, Physics Teacher, ACS International School Egham
What it maps
Six modules. Run only the one that fits your current unit.
M1
What Is a Force?
Force as something an object carries, and inertia treated as a force. Force mixed up with energy and momentum, doubt that a table can push, and system boundary errors.
14 questions · 5 clusters · ~15 min
M2
Newton's First & Second Laws
Force taken as proportional to velocity, acceleration mixed up with velocity, ma drawn as a force on diagrams, net force errors, and inertial frame mistakes.
14 questions · 5 clusters · ~15 min
M3
Weight, Gravity & Normal Force
Mass mixed up with weight, weightlessness myths, N = mg used everywhere, third-law pairing errors, and apparent weight confusion.
14 questions · 5 clusters · ~15 min
M4
Free-Body Diagrams
Missing forces, ghost forces, forces drawn on the wrong object, internal and external forces mixed up, and friction and tension errors.
14 questions · 5 clusters · ~15 min
M5
Applying Newton's Laws
Friction formula errors, sine and cosine swapped in components, N = mg on inclines, connected-object errors, and axis-choice mistakes.
14 questions · 5 clusters · ~15 min
M6
Newton's Third Law
Third-law pairs picked wrongly, the cancellation trap, confusion between equal interaction forces and their effects, and the third law in applied settings.
14 questions · 4 clusters · ~15 min
A question from it
Students who work hard still hold these ideas. They turn up in class after class.
The ghost force after the ball leaves the hand
Ask students to draw a free-body diagram of a ball thrown straight up, just after it leaves the hand. Many include an upward force of the throw. There is no such force. This impetus belief is one of the most common misconceptions in mechanics. Another force-diagram error is to add a centripetal force on top of the real inward force.
Normal force equals mg, always
Ask for the normal force on a block on an incline. Many students write N = mg. The same error appears on the floor of an accelerating lift. They have memorised the formula without the condition it depends on.
The Newton’s third law cancellation trap
Ask whether the weight of a book and the normal force on it form a third-law pair. Many students say yes, and add that the pair cancels. They have mixed up equilibrium with Newton’s third law, and the mix-up is hard to shift.
Constant force means constant velocity
Push a box across the floor at a steady speed. Many students say the push equals the net force, and that a force keeps an object moving. This is the old Aristotelian idea, and it hides behind correct answers on routine problems.
How it runs
Students use one shared link and need no logins.
Six modules of 14 questions, about 15 minutes each. Run only the module that fits your current unit.
The report arrives within 48 hours of your class finishing.
Request
Request a free pilot for your class
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Founding-department programme opens January 2027
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Arons, Knight and Hestenes document the misconceptions.