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UAT-UK SPEC: P3MODULE: PHYSICSTOPIC ID: ARCH-P-05

1D Coupled Multi-Body Resultant Force (Fₙₑₜ = ma), Lifts & Internal Tension

Master 1D Coupled Multi-Body Resultant Force (Fₙₑₜ = ma), Lifts & Internal Tension on the ESAT Physics paper. Traditional classroom derivations waste valuable seconds. Using the 2-step Sub-90 invariant elimination method compresses solve time to 40s, saving +110s per question.

Standard Classroom Time
150s
Textbook multi-line derivations bleed exam clock
Sub-90 Target Pace
40s
Comfortably below the 88.8s per-question limit
Time Saved for Review
+110s
Banks clock buffer across 27 questions

2-Step Sub-90 Shortcut Formula

How to eliminate intermediate algebra and solve under 45 seconds.

Launch Interactive Lesson
STEP 1 • SETUP INVARIANT (LINE 1)10–15s
Line 1 (Proportional Drag Check): Since 6001200=400800\frac{600}{1200} = \frac{400}{800}, resistive drag is proportional to mass and cancels from the internal tension split!

Establish the structural invariant and eliminate impossible options immediately.

STEP 2 • FAST SOLVE (LINE 2)15–25s
Line 2 (Mass Fraction): T=Fdrive×m2m1+m2=5000×8002000=2000 NT = F_{\text{drive}} \times \frac{m_2}{m_1 + m_2} = 5000 \times \frac{800}{2000} = 2000\text{ N} (25s).

Evaluate the simplified expression using integer factoring or unit elimination.

Distractor Trap Forensics

The predictable cognitive traps engineered by examiners into the wrong options.

TRAP #1subsystem_isolation_trap

Dividing driving force F by single mass m₁ instead of total coupled mass (m₁ + m₂) to find acceleration

Failing to treat the coupled blocks/train as a single system of mass (m₁ + m₂) when finding common acceleration a.

Sub-90 Fix: Test invariants before expanding equations.
TRAP #2sign_or_direction_flip

Writing normal contact force in an upward-accelerating lift as m(g - a) instead of m(g + a)

Subtracting upward acceleration from g instead of solving N - mg = ma => N = m(g + a).

Sub-90 Fix: Test invariants before expanding equations.
TRAP #3multi_statement_linchpin_foil

Claiming normal contact force and weight on the same object form a Newton's 3rd Law pair

Violating Newton's 3rd Law criteria (must act on two different bodies and be of the same physical force type).

Sub-90 Fix: Test invariants before expanding equations.

Try 1 Timed Question: 1D Coupled Multi-Body Resultant Force (Fₙₑₜ = ma), Lifts & Internal Tension

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Full Lesson All 15 Questions (ARCH-P-05)
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ARCH-P-05: 1D Coupled Multi-Body Resultant Force (Fₙₑₜ = ma), Lifts & Internal Tension (Sample)Physics
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SUB-90 ZONE (<40S)
0.0s40s Sub-9090s ESAT Budget150s Classroom
Question 1 of 1ARCH-P-05 (6-Card Lesson)Format: Standard 5-Option
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Question 1 of 1 • 90s Target

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