🧠 Introduction
Laws of motion describe the relationship between the motion of an object and the forces acting on it. These laws, formulated by Sir Isaac Newton, form the foundation of classical mechanics. This chapter explores inertia, force, momentum, and friction, and how they govern the motion of objects.
🧲 Force and Motion
Force: A push or pull acting on a body that can change its state of motion or shape.
Types of Forces:
Contact Force: Friction, tension, normal, spring, air resistance
Non-Contact Force: Gravitational, electric, magnetic
Characteristics:
Vector quantity (has magnitude and direction)
Measured in newton (N)
📜 Newton’s Laws of Motion
1️⃣ Newton’s First Law (Law of Inertia)
Statement: A body remains at rest or in uniform motion in a straight line unless acted upon by an external unbalanced force.
Key Concepts:
Inertia: Resistance of a body to change its state
Mass is a measure of inertia
Examples:
Passenger jerks forward when a bus suddenly stops
A book remains on a table until pushed
2️⃣ Newton’s Second Law (Law of Force)
Statement: 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.
Mathematical Form: 
Where:
= Force (N)
= Mass (kg)
= Acceleration (m/s^2)
Momentum: 
Applications:
Hitting a ball with a bat
Kicking a football
3️⃣ Newton’s Third Law (Action-Reaction Law)
Statement: For every action, there is an equal and opposite reaction.
Features:
Forces act on different bodies
Equal in magnitude, opposite in direction
Examples:
Gun recoils when fired
Walking (foot pushes ground, ground pushes foot)
📊 Impulse
Impulse (J): Product of force and time for which it acts 
Units: Ns or kg·m/s
Applications:
Airbags in cars
Catching a cricket ball with soft hands
🛠️ Friction
Definition: A force opposing the relative motion between two surfaces in contact.
Types:
Static Friction: Before motion starts
Kinetic Friction: During motion
Sliding friction
Rolling friction
Laws of Friction:
Proportional to normal reaction
Independent of area of contact
Opposes relative motion
Reducing Friction:
Lubrication
Ball bearings
📐 Circular Motion
Centripetal Force:
Acts towards the centre
Required for circular motion
Centrifugal Force (pseudo-force in rotating frame):
Appears to act outward in circular motion
📌 Equilibrium of Forces
Equilibrium: Net force and net torque on a body are zero
Static Equilibrium: At rest
Dynamic Equilibrium: In uniform motion
Free Body Diagrams (FBD):
Diagram showing all forces acting on a body
Essential for solving problems
📚 Practice Questions
A 10 kg object is subjected to a force of 20 N. What is its acceleration?
A bat hits a cricket ball of mass 0.2 kg giving it a velocity of 10 m/s in 0.1 s. Find the force exerted.
Draw a Free Body Diagram of a block on an inclined plane with friction.
A body moving in a circle of radius 2 m with speed 4 m/s. Find the centripetal force if mass = 5 kg.