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Playbook

Laws of Motion and Forces

41 q · 10% HARD. Newton's three laws (statements + applications), momentum conservation in collisions/recoil/explosions, impulse=Δp. The chapter that grew 3× in 2023–24.

questions in the bank
41
tagged HARD
10%
subtopic(s)
5
worked examples
2

When you’ll see it

A Newton's-laws statement-truth, a collision/recoil momentum conservation, an impulse from F-t graph, a friction-on-inclined-plane, or a 'two-equal-forces resultant' geometry.

How this chapter is tested

41 q in 10 years. Grew 3× in 2023–24 (typical 3–5 → 7, 10) — currently the second-most-tested chapter. Newton's three laws statement-truth (19 q) is the dominant subtopic. The work is recognising which law a scenario invokes: 1st (inertia, balanced forces), 2nd (F=ma, unbalanced), 3rd (action-reaction pairs).

Conservation of momentum (8 q) is the second pillar. m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ for isolated systems. Recoil: 0 = m_gun · v_gun + m_bullet · v_bullet — solve for v_gun (opposite-direction, much smaller because mass ratio). Elastic vs inelastic: elastic conserves KE too; inelastic loses KE to heat/deformation.

Impulse–momentum theorem: J = F·Δt = Δp. The recurring shape is the F-t graph — area under the curve equals impulse equals change in momentum. Trapezoidal area + initial v = 0 ⟹ final v = (impulse)/m.

The sub-skills

The rules and habits that decide whether you get a question right.

  • Newton's law recognition

    1st: object at rest stays at rest unless acted upon. 2nd: F_net = ma. 3rd: action-reaction pairs, EQUAL magnitude OPPOSITE direction on DIFFERENT bodies.

  • Momentum conservation in collisions

    Always conserved if no external force. Write m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ first, then check if KE also conserved (elastic) or not (inelastic).

  • Recoil equation

    Total initial momentum = 0 (system at rest). Final: 0 = m·v_object + M·V_recoil ⟹ V_recoil = −(m/M)·v_object. Opposite sign, scaled by mass ratio.

  • Impulse from F-t graph

    J = area under F-t curve. For a trapezoid (rises, plateau, falls), J = (sum of parallel sides)/2 × height — same as area-of-trapezoid. Δp = J ⟹ v_final = v_initial + J/m.

2 worked examples from the bank

Real past-year questions illustrating the playbook. Click to reveal options + solution.

Example 1Laws of Motion and ForcesHARD
Two forces of equal magnitude simultaneously act at a point. It is observed that the resultant force is equal in magnitude to the individual forces. Which of the following statements is/are correct? I. The angle between one of the individual forces and the resultant force is π/3\pi/3. II. The angle between the individual forces is 2π/32\pi/3. Select the answer using the code given below.

[Q52 · Apr · 2026]

Example 2Laws of Motion and ForcesHARD
A ball of 0.1 kg mass is dropped from height 0.45 m and rises to height 0.20 m. In contact with floor for 0.1 s. The net force applied on the floor while bouncing is (g = 10 m s−2s^{-2}) :

[Q86 · Apr · 2024]

Traps to expect

Distractor shapes specific to this chapter. The page-wide Traps section covers the bank-level patterns.

  • Action-reaction pair on same body

    Action-reaction NEVER acts on the same body. Book-on-table: gravity ON book (Earth-on-book) and Normal force ON book (table-on-book) are NOT action-reaction (both on book). The action-reaction PAIR for gravity-on-book is book-on-Earth.

  • Forgetting friction direction

    Kinetic friction opposes RELATIVE motion. On a block sliding down an incline, friction acts UP the incline. On a block being pushed, friction acts OPPOSITE the push.

Drill every laws of motion and forces question

41 questions from the bank, scoped to 5 bundled subtopics.

Drill the 41 questions

Related playbooks

Often paired with this one — drill these next if you found the worked examples above tractable.