Newton’s Laws of Motion: Complete Revision Notes for JKSSB FAA
Introduction
Newton’s Laws of Motion form the foundation of classical mechanics and are among the most important topics in the General Science section of the JKSSB Finance Accounts Assistant (FAA) examination. Questions from this topic are frequently asked in competitive exams because they test a candidate’s understanding of basic physical principles that govern the motion of objects in everyday life.
Developed by Sir Isaac Newton in the 17th century, these three laws explain how forces affect the motion of bodies. From a moving vehicle and a flying cricket ball to the launch of rockets into space, Newton’s Laws help us understand countless phenomena around us. For JKSSB FAA aspirants, it is essential to understand the concepts of force, inertia, acceleration, momentum, and action-reaction forces, as these are common areas from which objective-type questions are framed.
In this article, we will cover Newton’s First, Second, and Third Laws of Motion in a simple and exam-oriented manner, along with important formulas, real-life examples, and quick revision points to help you score better in the General Science section of the JKSSB FAA examination.
What is Force?
Before understanding Newton’s Laws of Motion, it is important to know the concept of force, as all three laws are based on how forces act on objects.
A force is a push or pull acting on an object that can change its state of rest, state of motion, direction, shape, or size. In simple terms, whenever we push, pull, lift, throw, or stop an object, we are applying force.
Definition of Force
Force is an external agent that changes or tends to change the state of rest or uniform motion of an object.
SI Unit of Force
The SI unit of force is Newton (N).
One Newton is defined as the force required to produce an acceleration of 1 m/s² in a body of mass 1 kilogram.
Formula:
Force (F) = Mass (m) × Acceleration (a)
F = ma
Types of Forces
1. Balanced Forces
When two or more forces acting on an object are equal in magnitude and opposite in direction, the net force becomes zero. Such forces are called balanced forces.
Effects of Balanced Forces:
- Do not change the state of motion of an object.
- An object at rest remains at rest.
- A moving object continues to move with the same speed.
Example: A book lying on a table experiences gravitational force downward and an equal upward force from the table.
2. Unbalanced Forces
When the forces acting on an object are not equal, the net force is not zero. Such forces are called unbalanced forces.
Effects of Unbalanced Forces:
- Can start or stop motion.
- Can change speed.
- Can change direction of motion.
Example: Kicking a stationary football causes it to move because an unbalanced force acts on it.
Key Points
- Force is a vector quantity (has magnitude and direction).
- SI unit of force = Newton (N).
- Balanced forces do not change motion.
- Unbalanced forces produce acceleration.
- Newton’s Laws of Motion explain the effects of force on objects.
Quick Revision
| Concept | Key Point |
| Force | Push or pull acting on an object |
| SI Unit | Newton (N) |
| Formula | F = ma |
| Balanced Forces | Net force = 0 |
| Unbalanced Forces | Net force ≠ 0 |
| Nature of Force | Vector Quantity |
Newton’s First Law of Motion (Law of Inertia)
Newton’s First Law of Motion explains why an object at rest remains at rest and why a moving object continues to move unless an external force acts upon it. This law is also known as the Law of Inertia because it is based on the concept of inertia.
Statement of Newton’s First Law
“A body continues to remain at rest or continues to move with uniform velocity in a straight line unless acted upon by an external unbalanced force.”
In simple words, an object will not change its state of rest or motion on its own. A force is required to change its condition.
Understanding the Law
- A stationary object remains stationary unless pushed or pulled.
- A moving object continues moving with the same speed and direction unless a force acts on it.
- The greater the mass of an object, the greater its resistance to change.
Concept of Inertia
Inertia is the natural tendency of an object to resist any change in its state of rest or motion.
Every object possesses inertia. It depends directly on the mass of the object.
Key Point: Greater the mass, greater the inertia.
Types of Inertia
1. Inertia of Rest
It is the tendency of a body to remain at rest.
Example: When a stationary bus suddenly starts moving, passengers tend to fall backward because their bodies try to remain at rest.
2. Inertia of Motion
It is the tendency of a moving body to continue moving with the same velocity.
Example: When a moving bus stops suddenly, passengers tend to fall forward because their bodies continue moving.
3. Inertia of Direction
It is the tendency of a body to resist a change in the direction of motion.
Example: Passengers lean sideways when a vehicle takes a sharp turn.
Key Exam Points
- Newton’s First Law is also called the Law of Inertia.
- Inertia is the resistance to change in the state of motion or rest.
- Inertia depends on mass.
- Larger mass means greater inertia.
- An external unbalanced force is necessary to change the state of an object.
Quick Revision
| Concept | Key Point |
| First Law | Law of Inertia |
| Inertia | Resistance to change in state |
| Depends On | Mass of the body |
| More Mass | More Inertia |
| External Force | Required to change motion |
| Motion Without Force | Uniform velocity in a straight line |
Everyday Examples of Newton’s First Law
Newton’s First Law of Motion can be observed in many situations that we encounter in daily life. These examples help us understand the concept of inertia and are frequently asked in competitive examinations such as JKSSB FAA.
Passengers Fall Backward When a Bus Starts Suddenly
When a stationary bus starts moving suddenly, the lower part of the passenger’s body moves along with the bus, while the upper part tends to remain at rest due to inertia. As a result, the passenger falls backward.
Passengers Fall Forward When a Moving Bus Stops Suddenly
When a moving bus stops abruptly, the lower part of the passenger’s body comes to rest with the bus, but the upper part continues moving forward due to inertia of motion. Therefore, the passenger falls forward.
Dust Comes Out When a Carpet Is Beaten
When a carpet is struck with a stick, the carpet moves suddenly while the dust particles tend to remain at rest due to inertia. As a result, the dust gets separated and falls off.
Fruits Fall When Tree Branches Are Shaken
When a branch is shaken suddenly, the branch moves but the fruits tend to remain at rest due to inertia. This causes the fruits to detach and fall to the ground.
Coin and Card Experiment
If a card placed over a glass is pulled quickly, the coin placed on the card falls straight into the glass. The coin tends to remain at rest due to inertia while the card moves away.
Use of Seat Belts in Vehicles
When a vehicle stops suddenly, passengers tend to move forward because of inertia of motion. Seat belts provide the necessary force to stop the body safely and prevent injuries.
Real-Life Applications of Inertia
- Seat belts in cars.
- Headrests in vehicles.
- Shaking clothes to remove dust.
- Harvesting fruits by shaking branches.
- Safety features in transportation systems.
Important Exam-Oriented Examples
Questions related to the following examples are commonly asked in competitive examinations:
- Passenger falling backward when a bus starts.
- Passenger falling forward when a bus stops.
- Dust particles separating from carpets.
- Coin-and-card experiment.
- Fruits falling from shaken trees.
- Use of seat belts.
Quick Revision
| Situation | Type of Inertia |
| Bus starts suddenly | Inertia of Rest |
| Bus stops suddenly | Inertia of Motion |
| Passenger leans during turn | Inertia of Direction |
| Dust from carpet | Inertia of Rest |
| Coin falls into glass | Inertia of Rest |
| Seat belt protection | Inertia of Motion |
Exam Tip: Whenever a question involves an object resisting a change in its state of rest, motion, or direction, the correct concept is usually inertia, which is explained by Newton’s First Law of Motion.
Newton’s Second Law of Motion
Newton’s Second Law of Motion explains how the motion of an object changes when a force acts on it. While the First Law describes the conditions for maintaining motion, the Second Law tells us how much motion changes when a force is applied.
Statement of Newton’s Second Law
“The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force.”
In simple words, a greater force produces a greater acceleration, while a heavier object requires more force to achieve the same acceleration.
Mathematical Expression
Newton’s Second Law is mathematically expressed as:
Force = Mass × Acceleration
F = ma
Where:
- F = Force (Newton, N)
- m = Mass (kilogram, kg)
- a = Acceleration (m/s²)
This equation is one of the most important formulas in physics and is frequently asked in competitive examinations.
Relationship Between Force, Mass, and Acceleration
Force and Acceleration
Acceleration is directly proportional to force.
- Greater force produces greater acceleration.
- Smaller force produces smaller acceleration.
Example: A football moves faster when kicked harder.
Mass and Acceleration
Acceleration is inversely proportional to mass.
- Greater mass produces smaller acceleration.
- Smaller mass produces greater acceleration.
Example: It is easier to push a bicycle than a loaded truck.
Understanding the Law Through an Example
Suppose two objects are pushed with the same force:
- A light object gains high acceleration.
- A heavy object gains low acceleration.
Similarly, if the same object is pushed with increasing force, its acceleration also increases.
This shows that both force and mass determine the acceleration of an object.
Importance of Newton’s Second Law
- Defines the quantitative relationship between force and motion.
- Provides the formula for calculating force.
- Forms the basis of mechanics and engineering calculations.
- Explains why heavier objects require more effort to move.
Key Exam Points
- Newton’s Second Law gives the mathematical definition of force.
- Formula: F = ma
- SI unit of force is Newton (N).
- Acceleration increases with force.
- Acceleration decreases with mass.
- Force and acceleration act in the same direction.
Quick Revision
| Concept | Key Point |
| Newton’s Second Law | Explains change in motion due to force |
| Formula | F = ma |
| SI Unit of Force | Newton (N) |
| Force and Acceleration | Directly proportional |
| Mass and Acceleration | Inversely proportional |
| Direction of Acceleration | Same as applied force |
Momentum and Newton’s Second Law
Momentum is one of the most important concepts related to Newton’s Second Law of Motion. In fact, Newton originally stated his Second Law in terms of momentum rather than acceleration. Questions based on momentum are frequently asked in competitive examinations, including JKSSB FAA.
What is Momentum?
Momentum is the quantity of motion possessed by a moving object. It depends on both the mass and velocity of the object.
A heavier object moving at high speed has greater momentum than a lighter object moving slowly.
Formula of Momentum
Momentum is calculated as: Momentum (p) = Mass (m) × Velocity (v)
p = mv
Where:
- p = Momentum
- m = Mass of the object
- v = Velocity of the object
SI Unit of Momentum
The SI unit of momentum is: kg m/s
Momentum is a vector quantity, which means it has both magnitude and direction.
Relationship Between Momentum and Force
According to Newton’s Second Law:
Force is equal to the rate of change of momentum.
Mathematically,
Force = Change in Momentum / Time Taken
F = (p₂ − p₁) / t
Where:
- F = Force
- p₁ = Initial momentum
- p₂ = Final momentum
- t = Time interval
This means that a larger force causes a greater change in momentum in a shorter period of time.
How Force Changes Momentum
A force can change momentum by:
- Increasing velocity
- Decreasing velocity
- Changing the direction of motion
- Changing both speed and direction
Everyday Examples of Momentum
Cricket and Catching the Ball
A fielder moves his hands backward while catching a fast-moving cricket ball. This increases the time taken to stop the ball, reducing the force of impact.
Airbags in Cars
Airbags increase the time during which passengers come to rest during a collision. This reduces the force experienced by the passengers.
Hammering a Nail
A hammer moving at high speed has large momentum, allowing it to drive a nail into a wall.
Importance of Momentum
- Helps explain the effect of force on moving objects.
- Forms the basis of Newton’s Second Law.
- Used in understanding collisions and vehicle safety.
- Important for sports and engineering applications.
Key Exam Points
- Momentum is the product of mass and velocity.
- Formula: p = mv
- SI unit: kg m/s
- Momentum is a vector quantity.
- Force equals the rate of change of momentum.
- Greater momentum means greater resistance to stopping.
Quick Revision
| Concept | Key Point |
| Momentum | Quantity of motion |
| Formula | p = mv |
| SI Unit | kg m/s |
| Nature | Vector Quantity |
| Newton’s Second Law | Force = Rate of Change of Momentum |
| Depends On | Mass and Velocity |
Applications of Newton’s Second Law
Newton’s Second Law of Motion has numerous applications in daily life, transportation, sports, and engineering. It helps us understand how force affects the motion of objects and why different amounts of force are required in different situations.
Applications in Sports
Athletes use the principles of Newton’s Second Law to improve performance and achieve greater speed or distance.
Kicking a Football
A football travels farther and faster when kicked with greater force because a larger force produces greater acceleration.
Batting in Cricket
A batsman hits the ball with force to change its velocity and direction. The greater the applied force, the greater the change in motion.
Throwing a Javelin
A stronger throw produces more acceleration, allowing the javelin to travel a greater distance.
Applications in Transportation
Acceleration of Vehicles
Cars, buses, and motorcycles accelerate when the engine provides force. More engine power produces greater acceleration.
Heavy Trucks Require More Force
Since trucks have greater mass, they require more force to accelerate compared to smaller vehicles.
Braking Systems
Brakes apply force opposite to the direction of motion, reducing the vehicle’s momentum and bringing it to rest.
Vehicle Safety Features
Newton’s Second Law plays an important role in the design of safety devices.
Airbags
Airbags increase the time over which a passenger’s momentum changes during a collision. This reduces the force experienced by the passenger.
Seat Belts
Seat belts prevent passengers from moving forward suddenly during braking and help reduce injury by controlling the change in momentum.
Numerical Concepts Important for Exams
Students should remember the following relationships:
- Force is directly proportional to acceleration.
- Force is directly proportional to mass.
- Acceleration is inversely proportional to mass.
- Formula: F = ma
For example:
- If mass remains constant and force doubles, acceleration also doubles.
- If force remains constant and mass doubles, acceleration becomes half.
Key Exam Points
- Greater force produces greater acceleration.
- Greater mass requires greater force for the same acceleration.
- Airbags and seat belts are practical applications of Newton’s Second Law.
- Formula: F = ma
- Force changes the velocity and momentum of an object.
Quick Revision
| Application | Principle Involved |
| Kicking a football | Greater force, greater acceleration |
| Vehicle acceleration | Force produces motion |
| Heavy truck movement | More mass requires more force |
| Airbags | Reduce force during collision |
| Seat belts | Control change in momentum |
| Bicycle riding | Pedaling force increases acceleration |
Newton’s Third Law of Motion
Newton’s Third Law of Motion explains the interaction between two objects when a force is applied. It states that forces always occur in pairs. Whenever one object exerts a force on another object, the second object simultaneously exerts an equal force in the opposite direction.
Statement of Newton’s Third Law
“For every action, there is an equal and opposite reaction.”
This means that forces always act in pairs. If one body applies a force on another body, the second body also applies a force of the same magnitude but in the opposite direction.
Understanding Action and Reaction Forces
Consider two objects, A and B:
- Object A exerts a force on Object B (Action).
- Object B exerts an equal and opposite force on Object A (Reaction).
These two forces:
- Are equal in magnitude.
- Act in opposite directions.
- Act simultaneously.
- Act on different objects.
Characteristics of Action-Reaction Pairs
Equal Magnitude
The action force and reaction force are always equal in size.
Opposite Direction
The two forces act in opposite directions.
Simultaneous Action
Action and reaction occur at the same instant.
Different Objects
The two forces act on different bodies and therefore do not cancel each other.
Why Action and Reaction Do Not Cancel Each Other
Many students think that action and reaction cancel each other because they are equal and opposite. However, this is not true because they act on different objects.
For example, when a person pushes a wall:
- The person exerts a force on the wall.
- The wall exerts an equal force on the person.
Since the forces act on different bodies, they do not cancel each other.
Importance of Newton’s Third Law
- Explains how movement occurs.
- Helps understand walking, swimming, flying, and rocket propulsion.
- Forms the basis of many engineering and transportation applications.
- Explains force interactions between objects.
Key Exam Points
- Newton’s Third Law is known as the Law of Action and Reaction.
- Every action has an equal and opposite reaction.
- Action and reaction forces are equal in magnitude.
- They act in opposite directions.
- They act on different objects.
- They occur simultaneously.
Quick Revision
| Concept | Key Point |
| Third Law | Law of Action and Reaction |
| Action Force | Applied by first object |
| Reaction Force | Applied by second object |
| Magnitude | Equal |
| Direction | Opposite |
| Time of Occurrence | Simultaneous |
| Act On | Different objects |
Exam Tip
Whenever a question involves walking, swimming, flying, pushing, jumping, or rocket motion, the underlying principle is usually Newton’s Third Law of Motion. Remember the statement: “For every action, there is an equal and opposite reaction.”
Everyday Examples of Newton’s Third Law
Newton’s Third Law of Motion can be observed in many activities that occur around us every day. These examples clearly demonstrate how action and reaction forces work together to produce motion.
Walking on the Ground
When we walk, our feet push the ground backward. This is the action force.
In response, the ground pushes our feet forward with an equal and opposite force. This is the reaction force that moves us forward.
Swimming
A swimmer pushes water backward using their hands and feet.
- Action: The swimmer pushes water backward.
- Reaction: Water pushes the swimmer forward.
This reaction force enables the swimmer to move through water.
Rowing a Boat
When the oars push water backward, the water exerts an equal and opposite force on the boat.
As a result, the boat moves forward.
Recoil of a Gun
When a bullet is fired from a gun:
- Action: The gun exerts a force on the bullet, causing it to move forward.
- Reaction: The bullet exerts an equal and opposite force on the gun, causing it to move backward.
This backward movement is known as recoil.
Rocket Propulsion
Rocket motion is one of the most important applications of Newton’s Third Law.
- Action: Hot gases are expelled downward at high speed from the rocket.
- Reaction: The rocket moves upward with an equal and opposite force.
Even in space, rockets can move because they carry and eject their own gases.
Jumping from a Boat
When a person jumps forward from a stationary boat:
- The person pushes the boat backward.
- The boat moves backward while the person moves forward.
This happens due to the action-reaction force pair.
Birds Flying in the Air
Birds push air downward with their wings.
The air pushes the birds upward, allowing them to fly.
Important Real-Life Applications
- Walking and running
- Swimming
- Rowing boats
- Rocket launches
- Flying aircraft and birds
- Recoil of guns
- Jumping from boats
Key Exam Points
- Walking is possible because the ground pushes us forward.
- Swimming occurs because water exerts a reaction force.
- Rockets move by expelling gases backward.
- Recoil is a common example of Newton’s Third Law.
- Action and reaction forces always act on different bodies.
Quick Revision
| Activity | Action | Reaction |
| Walking | Foot pushes ground backward | Ground pushes person forward |
| Swimming | Swimmer pushes water backward | Water pushes swimmer forward |
| Rowing a boat | Oars push water backward | Water pushes boat forward |
| Recoil of gun | Gun pushes bullet forward | Bullet pushes gun backward |
| Rocket launch | Gases move downward | Rocket moves upward |
| Bird flight | Wings push air downward | Air pushes bird upward |
Comparison of Newton’s Three Laws of Motion
Newton’s Three Laws of Motion are closely related, but each law explains a different aspect of motion and force. Understanding the differences between these laws is important for quick revision and solving objective questions in competitive examinations.
Newton’s First Law
The First Law explains the tendency of an object to maintain its current state of rest or motion unless acted upon by an external unbalanced force.
Main Concept: Inertia
Key Idea: Objects resist changes in their state of motion.
Newton’s Second Law
The Second Law explains how a force changes the motion of an object. It establishes a mathematical relationship between force, mass, and acceleration.
Main Concept: Force and Acceleration
Key Idea: Greater force produces greater acceleration.
Newton’s Third Law
The Third Law explains the interaction between two objects. It states that every action force is accompanied by an equal and opposite reaction force.
Main Concept: Action and Reaction
Key Idea: Forces always occur in pairs.
Quick Comparison Table
| Feature | First Law | Second Law | Third Law |
| Also Known As | Law of Inertia | Law of Acceleration | Law of Action and Reaction |
| Main Concept | Inertia | Force and Acceleration | Action-Reaction Forces |
| Explains | Why motion remains unchanged | How motion changes | Interaction between objects |
| Mathematical Form | No specific formula | F = ma | Action = Reaction |
| Depends On | Inertia | Force, Mass, Acceleration | Force Pairs |
| Example | Passenger falls backward when bus starts | Kicking a football | Rocket propulsion |
Key Differences at a Glance
First Law
- Deals with the state of rest or uniform motion.
- Introduces the concept of inertia.
- Explains why force is needed to change motion.
Second Law
- Gives the mathematical definition of force.
- Relates force, mass, and acceleration.
- Explains the rate of change of momentum.
Third Law
- Deals with force interactions between two bodies.
- States that forces occur in pairs.
- Explains action and reaction forces.
Importance for Competitive Exams
Questions are often asked to identify:
- Which law explains inertia.
- Which law gives the formula F = ma.
- Which law explains rocket motion.
- Which law is known as the Law of Action and Reaction.
- Which law explains the relationship between force and momentum.
One-Minute Revision
| Newton’s Law | Remember This |
| First Law | Inertia |
| Second Law | F = ma |
| Third Law | Action = Reaction |
Frequently Asked JKSSB Exam Concepts
Several concepts related to Newton’s Laws of Motion are repeatedly asked in JKSSB and other competitive examinations. A clear understanding of these topics can help you answer objective questions quickly and accurately.
Inertia
Inertia is the property of a body that resists any change in its state of rest, motion, or direction.
Key Facts:
- Inertia depends on mass.
- Greater mass means greater inertia.
- It is explained by Newton’s First Law of Motion.
Common Question: Which law of motion is known as the Law of Inertia?
Answer: Newton’s First Law of Motion.
Force
A force is a push or pull that can change the state of motion or rest of an object.
Key Facts:
- SI Unit: Newton (N)
- Force is a vector quantity.
- Formula: F = ma
Common Question: What is the SI unit of force?
Answer: Newton (N).
Momentum
Momentum is the quantity of motion possessed by a moving body.
Formula:
p = mv
Where:
- p = Momentum
- m = Mass
- v = Velocity
Key Facts:
- Momentum is a vector quantity.
- SI Unit: kg m/s
- Momentum increases with mass and velocity.
Common Question: Momentum is the product of which two quantities?
Answer: Mass and Velocity.
Acceleration
Acceleration is the rate of change of velocity with time.
Key Facts:
- SI Unit: m/s²
- Directly proportional to force.
- Inversely proportional to mass.
Common Question: Which law relates force, mass, and acceleration?
Answer: Newton’s Second Law of Motion.
Balanced and Unbalanced Forces
Balanced Forces
When forces acting on an object are equal and opposite, the net force becomes zero.
Effect: No change in the state of motion.
Unbalanced Forces
When forces are unequal, the net force is not zero.
Effect: Motion changes.
Common Question: Which type of force can change the motion of an object?
Answer: Unbalanced Force.
Action and Reaction
According to Newton’s Third Law:
“For every action, there is an equal and opposite reaction.”
Key Facts:
- Equal in magnitude.
- Opposite in direction.
- Act on different bodies.
- Occur simultaneously.
Common Question: Why do action and reaction forces not cancel each other?
Answer: Because they act on different objects.
SI Units
| Physical Quantity | SI Unit |
| Force | Newton (N) |
| Mass | Kilogram (kg) |
| Velocity | m/s |
| Acceleration | m/s² |
| Momentum | kg m/s |
Most Important One-Liners
- Newton’s First Law is known as the Law of Inertia.
- Newton’s Second Law gives the formula F = ma.
- Newton’s Third Law is known as the Law of Action and Reaction.
- Inertia depends upon mass.
- Momentum = Mass × Velocity.
- Force is the rate of change of momentum.
- SI unit of force is Newton.
- SI unit of momentum is kg m/s.
- Balanced forces do not change motion.
- Unbalanced forces produce acceleration.
Quick Revision Notes
Newton’s First Law of Motion
- Also known as the Law of Inertia.
- A body remains at rest or in uniform motion unless acted upon by an external unbalanced force.
- Inertia is the tendency of a body to resist change in its state of motion.
- Inertia depends on mass.
- Greater mass means greater inertia.
Types of Inertia
- Inertia of Rest: Resistance to change from rest.
- Inertia of Motion: Resistance to change from motion.
- Inertia of Direction: Resistance to change in direction.
Newton’s Second Law of Motion
- The rate of change of momentum is directly proportional to the applied force.
- Gives the mathematical definition of force.
- Formula:
F = ma
Where:
- F = Force
- m = Mass
- a = Acceleration
Momentum
- Momentum is the quantity of motion possessed by a body.
- Formula:
p = mv
Where:
- p = Momentum
- m = Mass
- v = Velocity
- SI Unit: kg m/s
- Momentum is a vector quantity.
Newton’s Third Law of Motion
- Also known as the Law of Action and Reaction.
- States that:
“For every action, there is an equal and opposite reaction.”
- Action and reaction forces:
- Are equal in magnitude.
- Act in opposite directions.
- Act on different bodies.
- Occur simultaneously.
Important SI Units
| Quantity | SI Unit |
| Force | Newton (N) |
| Mass | Kilogram (kg) |
| Velocity | m/s |
| Acceleration | m/s² |
| Momentum | kg m/s |
Frequently Asked Examples
| Situation | Concept |
| Passenger falls backward when bus starts | Inertia of Rest |
| Passenger falls forward when bus stops | Inertia of Motion |
| Dust leaves carpet when beaten | Inertia of Rest |
| Rocket launch | Newton’s Third Law |
| Recoil of a gun | Newton’s Third Law |
| Catching a cricket ball | Change in Momentum |
One-Line Facts for Exams
- Newton’s First Law = Law of Inertia.
- Newton’s Second Law = F = ma.
- Newton’s Third Law = Action and Reaction.
- Inertia depends on mass.
- Force is a vector quantity.
- Momentum is a vector quantity.
- Unbalanced force changes motion.
- Balanced forces do not change motion.
- SI unit of force is Newton.
- SI unit of momentum is kg m/s.
Conclusion
Newton’s Laws of Motion are among the most fundamental concepts in General Science and play an important role in competitive examinations such as JKSSB Finance Accounts Assistant (FAA). These laws explain why objects remain at rest, how forces change motion, and why forces always occur in pairs.
In this chapter, we learned about the concept of force, inertia, momentum, acceleration, and the practical applications of Newton’s Three Laws in everyday life. Understanding these concepts not only helps in solving examination questions but also enables us to explain many common phenomena such as walking, swimming, vehicle motion, recoil of a gun, and rocket propulsion.
For exam preparation, focus on the key formulas F = ma and p = mv, important SI units, real-life examples, and frequently asked MCQs. A thorough revision of these topics will help you answer questions quickly and accurately in the examination.
Remember:
- First Law → Inertia
- Second Law → F = ma
- Third Law → Action and Reaction
With regular practice and revision, Newton’s Laws of Motion can become one of the easiest and highest-scoring topics in the JKSSB FAA General Science syllabus.
Frequently Asked Questions (FAQs)
1. What is Newton’s First Law of Motion?
Newton’s First Law states that a body remains at rest or continues to move with uniform velocity in a straight line unless acted upon by an external unbalanced force. It is also known as the Law of Inertia.
2. What is inertia?
Inertia is the tendency of an object to resist any change in its state of rest, motion, or direction. The greater the mass of an object, the greater its inertia.
3. What is the formula of Newton’s Second Law of Motion?
The mathematical expression of Newton’s Second Law is:
F = ma
Where F is force, m is mass, and a is acceleration.
4. What is momentum?
Momentum is the quantity of motion possessed by a moving object and is calculated using:
p = mv
Where p is momentum, m is mass, and v is velocity.
5. What is the SI unit of force?
The SI unit of force is Newton (N).
6. What is the SI unit of momentum?
The SI unit of momentum is kg m/s (kilogram metre per second).
7. Why do passengers fall forward when a bus stops suddenly?
Passengers fall forward due to inertia of motion. Their bodies tend to continue moving even after the bus stops.
8. What is Newton’s Third Law of Motion?
Newton’s Third Law states:
“For every action, there is an equal and opposite reaction.”
It explains that forces always occur in pairs.
9. Why do rockets move upward?
Rockets move upward because they eject gases downward at high speed. According to Newton’s Third Law, the reaction force pushes the rocket upward.
10. Which topics from Newton’s Laws are most important for JKSSB FAA?
The most important topics include:
- Inertia and its types
- Force and its SI unit
- Newton’s Three Laws of Motion
- Momentum and its formula
- Action and Reaction forces
- Rocket propulsion
- Recoil of a gun
- Balanced and Unbalanced forces
- Frequently asked MCQs and numerical concepts
11. Which Newton’s Law gives the mathematical definition of force?
Newton’s Second Law of Motion gives the mathematical definition of force through the formula F = ma.
12. Which Newton’s Law is most frequently asked in competitive exams?
All three laws are important, but questions are most commonly asked from:
- Law of Inertia (First Law)
- Formula F = ma (Second Law)
- Action-Reaction Principle (Third Law)
- Real-life applications and SI units
About The Author
