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Class 9 Physics Chapter 3: Dynamics MCQs With Explanations
Practice Class 9 Physics Chapter 3: Dynamics MCQs with explanations for Pakistani board exams. Includes solved objective questions, answer checking, chapter revision guidance and next chapter suggestions.
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50Total MCQs
48With explanations
8Topics represented
Topics found: Impact Reduction, Walking Motion, Acceleration due to Gravity, Law of Gravitation, Gravitational Constant, Equilibrium, Tension Force, Action and Reaction
Q1. Fragile objects are packed with soft materials to:
Increasing the time of impact reduces the average force experienced, minimizing damage to fragile objects.
Q2. When a man walks on the ground, the force that enables him to move forward is:
Friction between the foot and the ground provides the necessary reaction force to propel the person forward.
Q3. The value of g (acceleration due to gravity) on earth's surface is approximately:
The standard value for acceleration due to gravity on Earth's surface is approximately 9.8 m/s².
Q4. According to Newton's law of gravitation, the force between two masses is:
Newton's law states that gravitational force is inversely proportional to the square of the distance between two masses.
Q5. The gravitational constant G has value:
The gravitational constant G is defined as 6.67 × 10⁻¹¹ N·m²/kg² in Newton’s law of universal gravitation.
Q6. A book lying on a table is in equilibrium because:
The book is in equilibrium because the downward gravitational force is balanced by the upward normal force from the table.
Q7. The force experienced by a rope when pulled is called:
Tension is the pulling force transmitted axially through a flexible connector like a rope or cable.
Q8. When you press a spring, the force exerted by your hand is called:
No explanation is available in the database for this MCQ yet.
Q9. The force that a surface exerts on an object lying on it, perpendicular to the surface, is called:
The normal force is the perpendicular contact force exerted by a surface to support the weight of an object.
Q10. Which instrument measures force directly in newtons?
A spring balance measures force via Hooke's law, where extension is proportional to applied force, and is calibrated in newtons.
Q11. The upward force exerted by a fluid on an object immersed in it is called:
Buoyancy is the upward force exerted by a fluid that opposes the weight of an immersed object.
Q12. A force that brings certain materials back to their original shape after deformation is called:
Elastic force is the restoring force exerted by a material to return to its original shape after deformation.
Q13. If mass of an object is 60 kg on earth, its mass on moon will be:
Mass is an intrinsic property and does not change with location; only weight changes due to gravity.
Q14. The weight of an object on moon is about _______ of its weight on earth.
The Moon's gravitational acceleration is approximately 1/6 of Earth's, so an object's weight on the Moon is about 1/6 of its weight on Earth, making option C correct.
Q15. Which of these is an example of rolling friction?
Rolling friction occurs when an object rolls over a surface, such as a ball rolling on the ground.
Q16. Streamlined shapes are used to reduce:
Streamlined shapes minimize air resistance by allowing fluid to flow smoothly around the object.
Q17. The force of friction can be reduced by:
Lubricants create a slippery layer between surfaces, minimizing direct contact and reducing frictional force.
Q18. Crumple zones in cars are designed to:
By increasing impact time, crumple zones reduce the average force experienced during a collision, enhancing safety.
Q19. A cricket player draws his hands backward while catching a ball to:
Increasing the time of impact reduces the average force experienced, as impulse is constant and force is inversely proportional to time.
Q20. When two bodies collide, their total momentum before collision equals their total momentum after collision if:
Momentum is conserved only when no external net force acts on the system, per the law of conservation of momentum.
Q21. The momentum of a 5 kg object moving at 2 m/s is:
Momentum is calculated as mass × velocity (5 kg × 2 m/s = 10 kg·m/s), making option B correct.
Q22. A force of 50 N acts on a mass of 10 kg. The acceleration produced is:
Newton's Second Law states F = ma, so a = F/m = 50 N / 10 kg = 5 m/s².
Q23. The force required to accelerate a 10 kg mass at 2 m/s² is:
Using F = ma, 10 kg × 2 m/s² = 20 N, which is the correct application of Newton’s second law.
Q24. When a fast-moving bus stops suddenly, passengers tend to fall forward due to:
Inertia is the tendency of a body to resist changes in its state of motion, causing passengers to continue moving forward.
Q25. The normal force is always:
The normal force is a contact force exerted by a surface to support the weight of an object resting on it, and it always acts perpendicular to the surface of contact.
Q26. In a free-body diagram, the forces are shown acting:
A free-body diagram isolates a single object and depicts all external forces acting on it, making it essential that all forces are shown acting on the same object for accurate analysis.
Q27. Which Pakistani scientist contributed to the unification of weak nuclear and electromagnetic forces?
Abdus Salam shared the 1979 Nobel Prize in Physics for developing the electroweak theory, unifying the weak nuclear and electromagnetic forces.
Q28. The force responsible for beta decay in atoms is the:
The weak nuclear force mediates beta decay by enabling the transformation of neutrons into protons and vice versa via emission of electrons or positrons.
Q29. The force that holds the nucleus of an atom together is the:
The strong nuclear force binds protons and neutrons in the nucleus, overcoming electrostatic repulsion between protons.
Q30. Which of the following is the weakest fundamental force?
Gravitational force is the weakest of the four fundamental forces, significantly weaker than the weak nuclear force.
Q31. The constant speed reached by a falling object when air resistance equals its weight is called:
Terminal velocity occurs when the downward force of gravity is balanced by upward air resistance, resulting in zero net force and constant speed.
Q32. Ball bearings are used to reduce:
Ball bearings replace sliding friction with rolling friction, thereby reducing the overall frictional resistance between moving parts.
Q33. Which type of friction is the strongest?
Static friction is the strongest because it prevents the initiation of motion between surfaces in contact.
Q34. The principle of conservation of momentum states that the total momentum of a system:
In the absence of external forces, the total momentum of a closed system remains constant over time.
Q35. The product of force and time is called:
Impulse is defined as the product of force and the time interval over which it acts, equaling the change in momentum.
Q36. When a bullet is fired from a gun, the gun recoils. This is an example of:
Newton's third law states that for every action, there is an equal and opposite reaction, explaining the recoil.
Q37. The force that helps a parachutist descend safely is:
Air resistance opposes gravity, reducing terminal velocity and enabling a safe, controlled descent.
Q38. One newton is the force that produces an acceleration of 1 m/s² in a mass of:
One newton is defined as the force required to accelerate a mass of 1 kg at 1 m/s², according to Newton's second law (F = ma).
Q39. The mass of a body is measured using a:
A physical balance directly compares an object's mass against standard masses, while spring balances and force meters measure weight (the gravitational force on an object).
Q40. Which device measures weight by detecting the force of gravity acting on a body through spring extension?
A spring balance measures weight by Hooke's law, where the extension of a spring is proportional to the gravitational force acting on the mass.
Q41. The force that opposes the relative motion between two surfaces in contact is called:
Friction is the resistive force that opposes relative motion between two surfaces in contact.
Q42. Which of the following is a non-contact force?
Gravitational force acts at a distance without physical contact, unlike friction, tension, or air resistance which require direct interaction.
Q43. Newton's third law of motion deals with:
Newton's third law states that for every action, there is an equal and opposite reaction, meaning forces always occur in pairs between two interacting bodies.
Q44. The momentum of a body is defined as the product of its:
Momentum is the product of mass and velocity, as defined by p = mv.
Q45. According to Newton's second law of motion:
No explanation is available in the database for this MCQ yet.
Q46. The force of gravity acting on an object is called its:
Weight is the force of gravity acting on an object, proportional to its mass and gravitational acceleration.
Q47. Which of the following is a contact force?
Frictional force requires direct physical contact between surfaces, making it a contact force, unlike the non-contact forces listed.
Q48. Newton's first law of motion is also known as the law of:
Newton's first law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force, which is the definition of inertia.
Q49. The SI unit of force is:
The SI unit of force is the Newton, defined as the force required to accelerate 1 kg at 1 m/s².
Q50. The property of a body to resist any change in its state of rest or motion is called:
Inertia is the inherent property of matter that opposes changes in motion, as defined by Newton's first law of motion.
After Chapter 3: Dynamics, Practice Next Chapters
Once you finish these MCQs, continue with the next available chapters from Physics so your revision stays chapter-wise and complete.
Complete the MCQs first, then review every incorrect answer against the textbook heading where that concept appears. For biology and other science subjects, pay attention to terminology, diagrams, sequence of processes, examples and differences between similar structures or functions.
This chapter page keeps the exact class, subject, chapter, question count, answer checking, explanations and follow-up chapters together, so students can revise from one focused URL instead of searching through the full book again.
Class 9 Physics MCQ Preparation: Dynamics
This page supports Matric Part 1 practice in Physics.
At this stage, the main purpose is building the definitions, symbols, rules and study habits needed for later matric work. The questions available here should be
used with the current textbook and the instructions issued by the learner's school or examination board.
What Physics MCQs can test
In Physics, objective questions commonly draw on definitions, physical quantities, SI units, laws, graphs, diagrams, formulas and the interpretation of numerical situations.
A useful answer is based on the exact wording and concept, not simply on recognising a familiar option.
For this subject, learners should write the known quantities and units before choosing a formula, and distinguish a law from the example used to demonstrate it.
Dynamics: what to focus on
Relationships between physical quantities, direction, units, laws, graphs and the conditions under which an equation applies.
Sketch a simple situation or graph for difficult questions and check whether the selected option agrees with both the formula and the physical meaning.
Common mistakes for Class 9 learners
In this subject, frequent errors include mixing scalar and vector quantities, overlooking units, reversing cause and effect, or choosing a familiar formula without checking its conditions.
Separate new terms that look similar and connect every formula, rule or definition with at least one textbook example. When the page marks an answer as incorrect, the next step should be to identify
the mistaken idea and verify it, rather than memorising the displayed answer letter.
A practical revision routine
Read a small textbook section, answer a focused set of MCQs and correct the underlying idea before starting the next section. Before attempting the MCQs, review definitions, symbols, unit conversions, graph shapes, diagram labels and the meaning of each term in a formula.
Complete a manageable set without notes, check the result, and divide errors into missing knowledge,
misunderstood concepts and careless reading. Revise the appropriate section before repeating the chapter.
How to review Dynamics after the quiz
List the questions you missed from Dynamics and write the textbook heading
connected with each one. Explain the correct idea in your own words, then return later and answer a
fresh set. This gives the chapter page a clear purpose: finding specific weaknesses in
Physics rather than only collecting a score.
Accuracy and responsible use
Explanations are provided where they exist in the question bank, but educational databases can contain
incomplete or mistaken material. Confirm disputed answers with an authoritative textbook or teacher.
Ahmad Learning Hub provides a practice resource and does not claim that a question will appear in an
examination or that every available item represents an official board question.
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