Class 11 Physics - PUNJAB
Laws of Motion
The chapter Laws of Motion in Class 11 Physics builds upon the concepts of kinematics to explain why objects move. For Punjab (PSEB) students, this is a foundational chapter that introduces Newton's three laws of motion, the concept of momentum, the impulse-momentum theorem, and the law of conservation of linear momentum. You will also learn about friction, its types, and how to analyze the motion of bodies on inclined planes. Scoring well in this chapter is crucial for board exams as numerical problems related to pulleys, lifts, and connected bodies frequently appear.
Start Learning FreeKey Concepts
Newton's First Law of Motion
An object continues to remain at rest or in uniform motion along a straight line unless an external force acts on it. It defines inertia, which is the natural tendency of objects to resist changes in their state of motion.
Newton's Second Law of Motion
The rate of change of linear momentum of a body is directly proportional to the applied external force and takes place in the direction in which the force acts. Mathematically, it is expressed as F = ma.
Newton's Third Law of Motion
To every action, there is always an equal and opposite reaction. Forces always occur in pairs acting on two different bodies simultaneously.
Law of Conservation of Linear Momentum
The total linear momentum of an isolated system of interacting objects remains conserved if no external force acts on the system.
Friction
The opposing force that comes into play when one body moves or tends to move over the surface of another body. It includes static, limiting, and kinetic friction.
Important Formulas
Board Exam Info
In the Punjab (PSEB) Class 11 Physics board exams, the Laws of Motion chapter typically carries around 5 to 7 marks. Questions usually include a mix of conceptual short-answer questions (1-2 marks), derivations like the acceleration of a body on an inclined plane or recoil of a gun (3 marks), and numerical problems based on Newton's laws, friction, or connected bodies (3-5 marks).
Frequently Asked Questions
Why do action and reaction forces not cancel each other out?
Action and reaction forces do not cancel each other because they act on two different bodies, not on the same body.
Is friction a self-adjusting force?
Yes, static friction is a self-adjusting force because it increases in magnitude to match the applied force until it reaches its maximum limit, known as limiting friction.
What is the difference between mass and inertia?
Mass is the quantitative measure of inertia. Greater the mass of a body, greater is its inertia and more force is required to change its state of motion.
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