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Next exam on November 14 – 15, 2026:
All concepts

Newton's Laws of Motion

牛顿运动定律

Newton's first law and inertia, the second law and its use in both force-to-motion and motion-to-force problems, and the action–reaction relationship of the third law.

18 real-exam questions · 4 sittings23 in mock papers28 practice

Formulas

  • Newton's second law

    Law
    Fnet=maF_{\text{net}}=ma

    Applies when：Acceleration is along the net force; valid for macroscopic bodies at low speed in an inertial frame

  • Newton's third law

    Law
    F12=−F21F_{12}=-F_{21}

    Applies when：Action and reaction are equal and opposite but act on different bodies, so they never cancel

How the real exam tests it

Questions from real CSCA papers that test this concept. Work each one out before you open the answer.

  1. CSCA Physics December 2025 Past Paper
    On a smooth horizontal surface, an object of mass m=2 kg\mathrm { m } = 2 \mathrm {~kg} undergoes uniformly accelerated linear motion from rest under the action of a horizontal pulling force FF. If its displacement within 2 seconds is 8 m , then the magnitude of the horizontal pulling force FF is ().
    • A．10 N
    • B．6 N
    • C．8 N
    • D．2 N
    Show answer & solution

    Answer: C

    1 From rest with constant acceleration: s=(1/2)\mathrm { s } = ( 1 / 2 ) a t2\mathrm { t } ^ { 2 }. 2 8 m=0.5×a×(2 s)2=2a=>a=4 m/s28 \mathrm {~m} = 0.5 \times \mathrm { a } \times ( 2 \mathrm {~s} ) ^ { 2 } = 2 \mathrm { a } = > \mathrm { a } = 4 \mathrm {~m} / \mathrm { s } ^ { 2 }. 3  F=ma=2 kg×4 m/s2=8 N\mathrm {~F} = \mathrm { ma } = 2 \mathrm {~kg} \times 4 \mathrm {~m} / \mathrm { s } ^ { 2 } = 8 \mathrm {~N}.
    See it in the full CSCA Physics December 2025 Past Paper
  2. CSCA Physics March 2026 Past Paper
    An elevator decelerates downward at 1 m/s21 \mathrm {~m} / \mathrm { s } ^ { 2 }. A 50 kg person's force on the floor is ( g=10 m/s2g = 10 \mathrm {~m} / \mathrm { s } ^ { 2 } )
    • A．450 N
    • B．500 N
    • C．550 N
    • D．600 N
    Show answer & solution

    Answer: C

    Decelerating downward = upward acceleration (apparent overweight). Nmg=ma,N=m(g+a)=50×11=550 N\mathrm { N } \mathrm { mg } = \mathrm { ma } , \mathrm { N } = \mathrm { m } ( \mathrm { g } + \mathrm { a } ) = 50 \times 11 = 550 \mathrm {~N}. By Newton's 3rd law, force on floor is also 550 N . Answer: C.
    Take the full CSCA Physics March 2026 Past Paper — timed & graded
  3. CSCA Physics April 2026 Past Paper
    A 2 kg object on a horizontal surface is pulled by a 10 N horizontal force. The coefficient of kinetic friction is μ=0.2\mu = 0.2. The object's acceleration is (g=10 m/s2)\left( g = 10 \mathrm {~m} / \mathrm { s } ^ { 2 } \right)
    • A．6 m/s26 \mathrm {~m} / \mathrm { s } ^ { 2 }
    • B．3 m/s23 \mathrm {~m} / \mathrm { s } ^ { 2 }
    • C．4 m/s24 \mathrm {~m} / \mathrm { s } ^ { 2 }
    • D．5 m/s25 \mathrm {~m} / \mathrm { s } ^ { 2 }
    Show answer & solution

    Answer: B

    Friction f=μmg=0.2×2×10=4 Nf = \mu m g = 0.2 \times 2 \times 10 = 4 \mathrm {~N}. By Newton's second law, a=F−fm=10−42=3 m/s2a = \frac { F - f } { m } = \frac { 10 - 4 } { 2 } = 3 \mathrm {~m} / \mathrm { s } ^ { 2 }.
    Take the full CSCA Physics April 2026 Past Paper — timed & graded

Real-exam evidence

Recorded past-paper appearances are listed below; online verification is labelled separately.

18 questions across 4 sittings1 of 4 sittings available to verify free online

23 questions across 6 mock papers — our own papers, so a coverage signal rather than real-exam evidence

28 related practice questions availablePractise free: Newton's Laws of Motion

Sitting evidence comes from the CSCA past papers on record; questions whose original paper is missing are excluded, and sprint papers are deliberately not counted.

Glossary

acceleration

Related concepts

Forces and EquilibriumCircular MotionGravitation and Satellites