📘 Chapter 3: Dynamics – Multiple Choice Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This section covers multiple choice questions from Chapter 3 Dynamics including Newton's laws of motion, momentum, impulse, friction, and related concepts. Each question is presented with four options, an answer check button, and a detailed explanation. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 3: Dynamics
📋 Exercise Short Qs
📝 Short Qs
📖 Comprehensive Qs
🔢 Numerical Problems
✅ MCQs
✏️ Constructed Response
Dynamics covers force, Newton's laws, momentum, friction, and circular motion.
✅ Multiple Choice Questions & Answers (PECTAA 2026)
3.1 When we kick a stone, we get hurt. This is due to:
✅ Correct Answer: (D) reaction
For every action, there is always an equal and opposite reaction. When we kick a stone, the stone exerts an equal and opposite force on our foot, causing pain.
For every action, there is always an equal and opposite reaction. When we kick a stone, the stone exerts an equal and opposite force on our foot, causing pain.
3.2 An object will continue its motion with constant acceleration until:
✅ Correct Answer: (B) the resultant force on it is zero
According to Newton's first law, an object continues its motion with constant velocity (zero acceleration) when net force is zero. If the net force is zero, acceleration is zero, so velocity remains constant.
According to Newton's first law, an object continues its motion with constant velocity (zero acceleration) when net force is zero. If the net force is zero, acceleration is zero, so velocity remains constant.
3.3 Which of the following is a non-contact force?
✅ Correct Answer: (C) Electrostatic force
Electrostatic force acts between two charged objects without physical contact. Friction, air resistance, and tension are contact forces.
Electrostatic force acts between two charged objects without physical contact. Friction, air resistance, and tension are contact forces.
3.4 A ball with initial momentum p hits a solid wall and bounces back with the same velocity. Its momentum p' after collision will be:
✅ Correct Answer: (B) p' = -p
Momentum is a vector quantity. When the ball bounces back with the same speed, the direction of velocity (and hence momentum) reverses. Therefore, p' = -p.
Momentum is a vector quantity. When the ball bounces back with the same speed, the direction of velocity (and hence momentum) reverses. Therefore, p' = -p.
3.5 A particle of mass m moving with velocity v collides with another particle of the same mass at rest. The velocity of the first particle after collision is:
✅ Correct Answer: (C) 0
In an elastic collision of equal masses where one is at rest, the moving mass stops completely (velocity = 0) and transfers all its momentum to the stationary mass.
In an elastic collision of equal masses where one is at rest, the moving mass stops completely (velocity = 0) and transfers all its momentum to the stationary mass.
3.6 Conservation of linear momentum is equivalent to:
✅ Correct Answer: (C) Newton's third law of motion
Conservation of momentum is derived from Newton's third law (action-reaction pairs). The internal forces between interacting bodies are equal and opposite, so the total momentum remains constant.
Conservation of momentum is derived from Newton's third law (action-reaction pairs). The internal forces between interacting bodies are equal and opposite, so the total momentum remains constant.
3.7 An object with mass 5 kg moves at constant velocity of 10 ms⁻¹. A constant force acts for 5 s and gives it a velocity of 2 ms⁻¹ in opposite direction. Force acting is:
✅ Correct Answer: (C) -12 N
Using \(F = ma = m\left(\frac{v_f - v_i}{t}\right)\):
\(F = (5)\left(\frac{-2 - 10}{5}\right) = (5)\left(\frac{-12}{5}\right) = -12 N\)
The negative sign indicates the force is in the opposite direction.
Using \(F = ma = m\left(\frac{v_f - v_i}{t}\right)\):
\(F = (5)\left(\frac{-2 - 10}{5}\right) = (5)\left(\frac{-12}{5}\right) = -12 N\)
The negative sign indicates the force is in the opposite direction.
3.8 A large force acts on an object for a short time. In this case, it is easy to determine:
✅ Correct Answer: (C) product of force and time
Impulse \(F \times \Delta t\) equals the change in momentum, which can be easily calculated from the change in velocity. The impulse-momentum theorem makes it easy to determine the product of force and time.
Impulse \(F \times \Delta t\) equals the change in momentum, which can be easily calculated from the change in velocity. The impulse-momentum theorem makes it easy to determine the product of force and time.
3.9 A lubricant is usually introduced between two surfaces to decrease friction. The lubricant:
✅ Correct Answer: (C) prevents direct contact of the surfaces
Lubricant creates a layer between surfaces, preventing direct contact and reducing friction. It does not act as ball bearings or provide rolling friction.
Lubricant creates a layer between surfaces, preventing direct contact and reducing friction. It does not act as ball bearings or provide rolling friction.
📐 Key Concepts – Dynamics (MCQs)
Newton's First Law: Inertia – body continues its state unless acted upon by a force.
Newton's Second Law: \(F = ma\). Acceleration is proportional to force and inversely to mass.
Newton's Third Law: Action and reaction are equal and opposite, acting on different bodies.
Momentum: \(p = mv\). Vector quantity.
Impulse-Momentum Theorem: \(F \Delta t = \Delta p\).
Conservation of Momentum: Derived from Newton's third law.
Friction: Lubricants reduce friction by preventing direct surface contact.
💡 Exam Tip:
For MCQs, read all options carefully before selecting an answer. Pay attention to key terms like "constant acceleration," "non-contact force," "vector quantity," and "impulse." Understanding the concepts behind Newton's laws, momentum, and friction will help you answer these questions correctly. These MCQs follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Chapter 1Physical Quantities and Measurements
Chapter 2Kinematics
Chapter 3✨ Dynamics
Chapter 4Turning Effect of Forces
Chapter 5Work and Energy
Chapter 6Mechanical Properties of Matter
Chapter 7Thermal Properties of Matter
Chapter 8Magnetism
Chapter 9Nature of Science
📖 Complete syllabus coverage for Class 9 Physics (PECTAA 2026) – Chapters 1 to 9
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus