Forces — free-body diagram of a stationary car: arrow lengths carry meaning
“Almost all candidates indicated an arrow for weight. Some omitted the normal contact force. The most common error was to have the lengths of the arrows for weight and normal contact force not equal.”
Set the length of each force arrow. The physics engine takes your diagram literally — if the arrows are unequal, the car accelerates. Make it sit still.
Only N = 12 kN keeps the car on the road: on a free-body diagram, equal lengths assert equal magnitudes. An examiner reads unequal arrows as a claim the car is accelerating.
Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H1 Physics 8867 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.
Made by lookang, using Claude Fable 5. More resources: iwant2study.org