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Laws of Motion Class 11 Physics Chapter 4 One Shot | New NCERT CBSE

LearnoHub - Class 11, 12・127 minutes read

Newton's Laws of Motion explain concepts of force, motion, and friction, with practical examples demonstrating the mathematical relationships between them. Understanding these laws is crucial for solving physics problems involving motion, friction, and pulley systems, emphasizing the key role of forces in various scenarios.

Insights

Newton's Laws of Motion, including the First and Second Laws, detail how objects behave in response to external forces, with inertia and momentum playing crucial roles in understanding motion.
Friction, a force that opposes motion, is essential in various scenarios, transitioning from static to kinetic forms and affecting objects' acceleration and velocity based on their mass and the applied force.
Pulley systems, both frictionless and with friction, provide practical examples of applying Newton's laws and understanding tension forces and accelerations in interconnected masses, aiding in problem-solving exercises.
Circular motion concepts, such as centripetal force and optimum velocity on banked roads, illustrate the intricate balance between friction, normal force, and acceleration in determining the maximum speed and safety of moving objects.

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Summary

00:00

Laws of Motion: Force, Inertia, and Acceleration

Newton's Law of Motion is being discussed in a Class 11 Physics lesson.
The concept of force and motion is explained using the example of a girl pulling a toy.
Aristotle's idea of resistive forces, like friction, opposing motion is introduced.
Friction is described as a force that stops objects from moving on their own.
Galileo's experiments on frictionless surfaces led to the concept of uniform motion without external forces.
Galileo's Law of Inertia states that a body in motion stays in motion on a frictionless surface.
Inertia is defined as a body's resistance to change its state of motion.
Practical examples of inertia, like feeling a jerk in a moving bus, are provided.
Newton's First Law of Motion states that a body at rest stays at rest, and a body in motion stays in motion unless acted upon by an external force.
Newton's Second Law of Motion introduces the mathematical relationship between force, mass, and acceleration, expressed as force = mass * acceleration.

14:49

Understanding Newton's Second Law of Motion

Moving from rest to motion involves considering the force required, with heavier objects needing more force to set them in motion compared to lighter ones.
The force needed to stop an object in motion is also dependent on its mass, with heavier objects requiring more force to stop them.
Objects moving at higher velocities require more force to stop them, as the force needed is inversely proportional to the velocity.
The concept of momentum is crucial, with the change in momentum directly related to the force required, which is dependent on both mass and velocity.
The rate of change in momentum determines the force needed, with rapid changes resulting in higher forces.
Newton's second law states that force is directly proportional to the rate of change of momentum, expressed as F = dp/dt.
The unit of force is the Newton, calculated as mass multiplied by acceleration, aligning with Newton's second law.
Newton's second law is consistent with the first law, as force is equal to mass multiplied by acceleration, with acceleration referring to the center of mass of larger bodies.
Newton's second law is a vector law, considering forces in x, y, and z components, applicable to all vector laws of addition.
The force at a specific point and instant is related to the acceleration at that same point and instant, crucial for calculating stopping forces and times in practical scenarios.

30:28

Physics Equations and Newton's Laws Explained

The equation to determine velocity is v = u + 2as.
The square of 10 is 100.
The acceleration value becomes negative when the car stops.
The force required to stop the car is mass multiplied by acceleration.
The stopping force is calculated to be 2 * 10^3 newtons.
The time taken to stop the car is found using the equation v = u + at, resulting in 10 seconds.
The force components of a 5kg object are given as fx = 15 newtons and fy = 25 newtons.
The acceleration of the object is calculated to be 5.83 meters per second square.
Impulse is defined as force multiplied by the time it acts over.
Newton's Third Law states that for every action, there is an equal and opposite reaction, with forces acting simultaneously on different bodies.

46:29

Momentum, Friction, and Contact Forces in Physics

The formula f12 p1 d - p1 divided by delta t equals minus of minus of p2 d minus p2 divided by delta t is discussed.
The concept of total initial momentum (p1 + p2) being equal to total final momentum (p1' + p2') is explained.
The idea of equilibrium in particles, where net external force is zero, is detailed.
A question involving a gun mounted on wheels shooting a projectile is presented, with initial and final velocities given for calculation.
A problem involving two trucks colliding and moving together with a common velocity is discussed, applying conservation of momentum.
Newton's three laws of motion are introduced, focusing on contact forces like friction, normal forces, tension forces, and spring forces.
Friction is explained as a force opposing relative motion between two surfaces in contact.
The existence of static friction, kinetic friction, and rolling friction is highlighted.
The role of external force in overcoming friction to initiate motion is emphasized.
The importance of understanding and applying contact forces in solving physics problems is stressed.

01:02:31

Friction: Static to Kinetic Transition and Types

Static friction opposes relative motion of a body at rest, transitioning to kinetic friction once motion begins.
Static friction reaches a maximum value and cannot increase further beyond a certain limit.
Applied force exceeding static friction's limiting value initiates body movement.
Kinetic friction comes into play once the body starts moving, opposing applied force.
Kinetic friction does not depend on velocity or contact area, but solely on normal force.
Applied force greater than kinetic friction accelerates the body, while equal force maintains uniform velocity.
When applied force is zero, kinetic friction halts body movement.
Static friction requires more effort to transition a body from rest to motion compared to maintaining motion, hence its value is greater than kinetic friction.
Rolling friction occurs when an object rolls on a surface, with the point of contact constantly changing.
Rolling friction opposes the motion of a rolling object by deforming surfaces at points of contact, with its value being the lowest among friction types.

01:19:10

"Friction in Movement: Tips and Techniques"

Walking involves applying a backward force on the ground and a forward force at our feet, leading to acceleration.
Friction is crucial for preventing slipping between our feet and the ground, enabling stability while walking.
Friction has both advantages and disadvantages, with benefits including facilitating movement for humans and machinery.
Lubricants and grease can reduce friction, making surfaces smoother and improving movement.
Ball bearings are effective in reducing friction by replacing sliding friction with rolling friction.
Design modifications, like tapering airplane fronts, can minimize friction and air resistance for efficient movement.
Understanding Newton's laws of motion is essential for comprehending friction and its impact on movement.
Solving physics numericals involves creating free body diagrams and writing equations of motion for objects.
Pulley systems with connected masses require considering tension forces and accelerations, especially in frictionless scenarios.
Tips and techniques for handling numerical problems include understanding pulley systems and addressing various scenarios involving friction and movement.

01:34:33

Comparing masses and forces in pulley scenario.

Frictionless pulley scenario discussed, with m1 and m2 masses compared.
Explanation of m1 and m2 movements based on their relative weights.
Acceleration of m1 and m2 in different scenarios detailed.
Impact of frictionless pulley on a1 and a2 values explained.
Motion of m1 and m2 in relation to their weights discussed.
Introduction to a scenario with two masses connected to a pulley.
Tension denoted as t1 and t2, with forces acting on m1 and m2 explained.
Analysis of horizontal and vertical forces acting on m1 and m2.
Practical example involving an automobile's speed and friction calculations.
Application of Newton's second law and kinetic equations to solve a vehicle stopping distance problem.

01:51:47

Calculating Forces and Acceleration in Physics

W2 is at the bottom of the table part, with a normal force acting upwards.
The equation for W2 is calculated as cry*l-l * g = n.
The goal is to determine the maximum length, sl, using the equations derived.
By dividing equation one by two, the value of l is found to be m / (1 + n).
The logic applied involves analyzing the hanging part and the forces acting on it.
Problem four involves a pulley system with blocks m1 and m2 connected by an extensible string.
The acceleration of the system and the tension in the string need to be calculated.
Equations are set up for m2 and solved to find the acceleration and tension values.
Problem five deals with a 4kg mass on an inclined plane at a 15° angle.
The coefficient of static friction is determined using equations and trigonometry.

02:09:25

Analyzing Equations for Acceleration in Physics

Equations are analyzed, t terms cancel out when added, leading to acceleration being equal to t times gravity divided by 3.
Acceleration is calculated as t times gravity divided by 3, resulting in meters per second squared.
The value of acceleration is determined by substituting 99.8 for gravity, solving the first part of the question.
Velocities of mass m moving up 5 meters are calculated, with initial velocity being zero and acceleration being gravity divided by 3.
The velocity of mass m is found to be 10 times gravity divided by 3 meters per second.
Newton's Laws of Motion are highlighted as crucial for problem-solving, particularly in kinetic equations.
The importance of kinetic equations in solving problems, especially pulley problems, is emphasized.
Circular motion is introduced, explaining the concept of centripetal force and its role in objects moving in circular paths.
The maximum speed of a car in circular motion on a level road is determined by the expression v is less than or equal to the square root of m times acceleration times radius times gravity.
The velocity of a car in circular motion on a banked road is calculated using equations involving friction, normal force, and acceleration.

02:27:36

"Optimum Velocity on Bank Roads Explained"

In circular motion on a bank road, the maximum velocity of a car cannot exceed the optimum velocity, which is the velocity when no frictional force is required to provide the centripetal force.
Optimum velocity is achieved when frictional force is unnecessary, indicating the end of its role in providing centripetal force, leading to reduced wear and tear on tires.
The optimum velocity on a bank road is calculated as the square root of the product of acceleration due to gravity, radius, and angle of inclination.
When the velocity exceeds the optimum velocity, friction comes into play to provide centripetal force, operating down the slope towards the center.
Friction is required when the velocity is less than the optimum velocity, operating up the slope, allowing for the vehicle to be parked on a bank road.
The maximum permissible force speed on a bank road can be calculated using a formula involving the radius, acceleration due to gravity, coefficient of friction, and angle of inclination, ensuring the car does not slip.

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