NCERT Class 9 · Physics

True–False Booster – Laws of Motion

Sharpen your intuition about Newton’s laws, inertia, friction, momentum and equilibrium using exam‑style True–False statements with reasoning.

Each statement in this set targets a specific conceptual pitfall – ideal for last‑minute self‑check before school tests and Olympiad‑level problems.

Concept Drills Quick Revision Reasoning Practice
Jump to True–False Questions
Laws of Motion
True–False Lab
Inertia
Action–Reaction
Friction & Equilibrium
Momentum & Impulse

Quick Snapshot – Chapter at a Glance

Chapter
4 · Force and Laws of Motion
Focus Here
Concept traps in T/F questions
Best Use
Warm‑up before numericals & MCQs

Why Laws of Motion & True–False Matter

Board Exams & School Tests

  • Short True–False and reason‑type questions are common for quick concept checking.
  • Misconceptions about “force needed to keep motion” and “action–reaction” cost easy marks.
  • Clear ideas here make later topics like work–energy, gravitation and motion in a plane simpler.

Entrance & Olympiad Foundation

  • Competitive exams test subtle points on friction, pseudo‑force, equilibrium and circular motion.
  • Statement‑based MCQs often mirror these True–False ideas with “correct/incorrect” patterns.
  • Strong reasoning now becomes a backbone for Class 11–12 mechanics questions.

Key Concept Highlights Behind the Statements

Equilibrium & Inertia

  • Net external force zero implies zero acceleration, not necessarily zero velocity.
  • A body can be in uniform motion and still be in mechanical equilibrium.
  • True–False items here test your feel for “state of motion” vs “forces on it”.

Action–Reaction & Internal vs External

  • Action–reaction forces act on different bodies and never appear together in one FBD.
  • Internal forces cannot change total momentum of a system; only external forces can.
  • Many T/F items subtly mix up internal, external and interaction forces.

Friction, Pseudo forces & Circular Motion

  • Static friction is self‑adjusting; limiting friction and kinetic friction have fixed formulae.
  • In uniform circular motion on a flat road, static friction provides centripetal force.
  • Pseudo force and COM motion appear in advanced True–False practice for deeper insight.

Important Formula Capsules

Force & Acceleration
\(F = m a\)
Momentum
\(p = m v\)
Impulse
\(J = F\,\Delta t = \Delta p\)
Static & Kinetic Friction
\(f_{\max} = \mu_s N,\quad f_k = \mu_k N\)
Centripetal
\(a_c = v^2/R,\quad F_c = m v^2/R\)
Pseudo Force (Advanced)
\(\vec{F}_{\text{pseudo}} = -m\vec{a}_{\text{frame}}\)

You will apply these in statements about equilibrium, friction, collisions, pseudo forces and circular motion without heavy calculations.

What You Will Practise with These True–False Items

  • Recognise whether zero net force means “at rest” or “constant velocity” in different contexts.
  • Decide correctly if a given situation is in mechanical equilibrium or not.
  • Identify whether a statement about action–reaction is correct (same line, different bodies, equal and opposite).
  • Distinguish internal and external forces when talking about conservation of momentum.
  • Judge when static friction adjusts and when limiting or kinetic friction is being used.
  • Relate F–t and p–t graphs to impulse and force, and use them to interpret impact questions.
  • Understand advanced statements about pseudo forces, COM motion and constraints in string–pulley systems.
  • Spot incorrect generalisations such as “normal reaction is always equal to weight” or “friction is always opposite to velocity”.

Navigate to Detailed Laws of Motion Notes

Core Ideas

Forces, Friction & Motion

Revision & Practice

Exam Strategy – Using True–False for Laws of Motion

  • 01
    Always justify your choice. When you mark a statement True or False, write one line of reasoning (law, formula or example) – this trains you for “reason‑type” questions.
  • 02
    Watch for hidden words like “always” or “only”. Many false statements fail because they ignore special cases such as non‑inertial frames, non‑horizontal surfaces or presence of external forces.
  • 03
    Link each statement to a diagram. Draw a quick free‑body diagram or motion sketch for statements about friction, tension, circular motion or recoil before deciding True/False.
  • 04
    Group statements by concept. Solve all inertia/equilibrium items together, then all friction items, then momentum/impulse – this deepens pattern recognition for exams.
  • 05
    Use these as a daily warm‑up. Attempt 5–10 True–False questions each day before numericals; you will gradually eliminate typical misconceptions before the actual exam.

Before the Test

  • Revise three laws, definitions of momentum, impulse, friction and equilibrium.
  • Scan through your solved True–False set and re‑check the ones you got wrong earlier.
  • Quickly glance at the “Common Mistakes” list to avoid last‑minute slips.

Start True–False Practice

Scroll down to the True–False questions section below. Use the statements such as “A body can remain in uniform motion even when several forces act on it simultaneously”, “Static friction can adjust its magnitude up to a certain maximum value”, “In uniform circular motion on a horizontal road, static friction provides the necessary centripetal force” and many more to test your understanding one concept at a time.

Your Progress 0 / 25 attempted
Q 01 / 25
If a constant force acts on a body and there is no displacement, then the work done by the force is zero.
Q 02 / 25
Work done by a force can be positive, negative or zero.
Q 03 / 25
Kinetic energy of a body depends only on its speed and not on the direction of motion.
Q 04 / 25
A body can possess energy even when its mechanical work per second (power) is zero.
Q 05 / 25
The SI unit of work and the SI unit of energy are the same.
Q 06 / 25
If a force is always perpendicular to the instantaneous displacement of a particle, then the work done by the force is zero.
Q 07 / 25
When a body falls freely under gravity in vacuum, the loss in potential energy is equal to the gain in kinetic energy at every instant (neglecting relativistic effects).
Q 08 / 25
A porter walking on a level road with a load on his head does positive work against gravity.
Q 09 / 25
The area under a force–displacement graph represents the work done by that force.
Q 10 / 25
If the net work done on a particle during its motion is zero, then its speed must remain constant.
Q 11 / 25
Power is defined as the work done per unit time, so it must always be constant for a given process.
Q 12 / 25
A conservative force is one for which the work done between two points depends only on the path taken.
Q 13 / 25
The work done by all conservative forces over any closed path is zero.
Q 14 / 25
In presence of non-conservative forces (like friction), the total mechanical energy of a system is always conserved.
Q 15 / 25
A satellite moving in a perfectly circular orbit around the Earth has constant kinetic energy and constant gravitational potential energy.
Q 16 / 25
For a body attached to an ideal spring obeying Hooke's law, the potential energy stored in the spring is proportional to the square of its extension.
Q 17 / 25
A body can have non-zero momentum but zero kinetic energy in classical mechanics.
Q 18 / 25
In an elastic collision between two particles, both kinetic energy and linear momentum of the system are conserved.
Q 19 / 25
In an inelastic collision, total mechanical energy of the system decreases, but total linear momentum of the system can still remain conserved.
Q 20 / 25
A heavier body always has more kinetic energy than a lighter body if both have the same linear momentum.
Q 21 / 25
If the net external work done on a system of particles is zero, then the velocity of the centre of mass of the system must remain constant.
Q 22 / 25
A variable force whose magnitude depends on position can never be treated using the work-energy theorem.
Q 23 / 25
For a particle subjected only to a one-dimensional conservative force, the motion can be described by imagining the particle sliding in an effective potential energy curve.
Q 24 / 25
The maximum speed of a particle executing vertical motion attached to a spring (neglecting air resistance) occurs at the extreme positions where its potential energy is maximum.
Q 25 / 25
In a central gravitational field, a bound orbit with total mechanical energy just less than zero corresponds to a nearly parabolic trajectory, which is highly sensitive to small changes in energy.
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