Laws of Motion NEET Notes | Newton's Laws, Free Body Diagrams, Friction

Laws of Motion NEET Notes

The Laws of Motion chapter is a fundamental topic in NEET Physics. It explains how objects move and interact based on applied forces. Understanding Newton’s Laws, inertia, momentum, impulse, and friction is crucial for solving numerical problems in the NEET exam.

Importance of Laws of Motion in NEET

• Forms the foundation for mechanics and motion-related topics.
• Includes Newton’s Laws of Motion, essential for problem-solving.
• Explains frictional forces, which play a key role in real-world applications.
• Helps in understanding concepts of impulse and momentum in collisions.

Basic Concepts in Laws of Motion

1. Newton’s First Law of Motion (Law of Inertia)

An object at rest stays at rest, and an object in motion stays in motion unless acted upon by an external force.

Inertia: The tendency of an object to resist changes in its motion.

Types of Inertia:

• Inertia of Rest: A stationary object remains at rest unless acted upon.
• Inertia of Motion: A moving object continues its motion in the same direction unless stopped.
• Inertia of Direction: An object moving in a straight path continues in the same direction unless an external force changes it.

2. Newton’s Second Law of Motion

The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.

Mathematical Form: F = ma
Where:

• F = Force (N)
• m = Mass (kg)
• a = Acceleration (m/s²)

3. Newton’s Third Law of Motion

For every action, there is an equal and opposite reaction.

Example: When you push against a wall, the wall pushes back with equal force.

Momentum and Impulse

Momentum (p): The product of mass and velocity.

Formula: p = mv

Impulse: The change in momentum due to an applied force over a short time.

Formula: Impulse = Force × Time = Δp

Free Body Diagram (FBD)

A free-body diagram is a graphical representation used to analyze forces acting on an object.

Steps to Draw FBD:

• Identify the object.
• Consider all forces acting on it (gravity, normal, friction, tension, etc.).
• Draw a diagram representing these forces.

Friction and Its Types

Friction is the force opposing the relative motion of two surfaces in contact.

Types of Friction:

• Static Friction: Prevents motion (stronger than kinetic friction).
• Kinetic Friction: Acts when an object is already in motion.
• Rolling Friction: Acts when an object rolls over a surface (lesser than sliding friction).

Key Formulas for Laws of Motion (NEET)

• Force: F = ma
• Momentum: p = mv
• Impulse: Impulse = F × Δt = Δp
• Coefficient of Friction: μ = Friction Force / Normal Force
• Work Done by a Force: W = F × d × cosθ

Why Study Laws of Motion for NEET?

• Frequently asked numerical and theoretical questions in NEET.
• Forms the base for advanced physics topics.
• Understanding friction, force, and free-body diagrams helps in real-world physics applications.

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