Work Energy and Power | Class 11 Physics Chapter 5 One Shot | New NCERT book CBSE

LearnoHub - Class 11, 12・2 minutes read

The text covers a wide range of physics topics, including work, energy, power, potential and kinetic energy, conservation laws, collisions, and calculations involving mass, velocity, force, and displacement, providing examples and equations to illustrate these concepts. It also delves into the conservation of linear momentum in elastic collisions, detailing equations to find final velocities and exploring special cases with equal or significantly different masses.

Insights

Physics terms like Work, Energy, and Power are integral in daily conversations, with Work defined as the effort to achieve a goal, Energy as the ability to do work (e.g., studying), and Power as the capacity to effectively use energy.
The text delves into the intricacies of Work, Energy, and Power, illustrating their applications through examples like negative work in a tug of war, the conversion of potential energy to kinetic energy in a bow and arrow, and the conservation of mechanical energy in systems like a dropping ball or a spring-ball scenario.

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What is work in physics?
Effort to achieve a purpose.

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Summary

00:00

Understanding Physics: Work, Energy, Power, Vectors

Physics terms: Work, Energy, Power are commonly used in daily life conversations.
Introduction to Class 11th Physics Work Energy Power One Short video on Lan Hup Free Learning Platform.
Understanding the meaning of work in everyday life as physical or mental effort to achieve a purpose.
Energy defined as the strength to do work, like studying to perform well.
Power explained as the capacity or ability to make efforts and use energy effectively.
Introduction to scalar product of vectors in physics to understand work, energy, and power.
Properties of scalar product including commutative and distributive laws.
Special cases like dot product of equal vectors resulting in square of the vector.
Significance of dot product of vectors resulting in zero indicating perpendicularity.
Physics definition of work as force causing displacement of an object, denoted by scalar product of force and displacement.

16:44

Understanding Work, Energy, and Kinetic Principles

Negative work occurs when the direction of force and displacement are opposite.
Tug of war is a common example of negative work, where forces are applied in different directions.
Friction is essential for walking, preventing slipping and aiding in forward motion.
Work done can be graphically represented by the area under a force-displacement graph.
The formula for work is force multiplied by displacement, or the dot product of force and displacement.
To calculate work done to stop a lorry, mass, initial velocity, final velocity, and time are crucial.
Kinetic energy is the energy of a moving object, calculated as 1/2 * mass * velocity^2.
Hydroelectricity harnesses the kinetic energy of flowing water to generate electricity.
The Work-Energy Theorem states that work done on an object equals the change in kinetic energy.
Potential energy is energy by virtue of position, such as the potential energy experienced on swings at amusement parks.

32:04

Potential Energy Conversion in Physics Explained

Potential energy converts to kinetic energy when an object is released from a height.
The example of a bow and arrow from Ramayana and Mahabharata illustrates potential energy conversion.
Stretching a string stores potential energy in an arrow before release.
Conservative forces store potential energy in an object's configuration.
Removing external constraints converts potential energy to kinetic energy.
Mathematical calculations prove the conversion of potential energy to kinetic energy.
Conservation of Mechanical Energy states that total mechanical energy remains constant in a system.
The example of dropping a ball from a height demonstrates conservation of mechanical energy.
Another example with spring force shows how work is done in relation to displacement.
Hooke's Law explains the proportional relationship between spring force and displacement.

50:40

Spring Force Integration and Work Calculation

Integration of x dx2 results in x^2/2
Work done is -k*a*m*s^2
Displacement and spring force directions differ
Work done is calculated as -k*x^2/2
Work done by spring force in a cyclical process is 0
Spring force is conservative
Conservation of Mechanical Energy in Spring Ball case
Total mechanical energy at any point x is kinetic energy + potential energy
Maximum displacement x results in total mechanical energy of 1/2kms
Maximum velocity is √(k/m)

01:09:41

Calculating Power, Momentum, and Energy in Physics

The text discusses the concept of height, velocity, and power in relation to mass and acceleration.
It explains the calculation of mass based on given values and the concept of velocity as height covered per unit time.
The text delves into a practical question involving the mass of a car traveling at a certain speed and coming to rest at a specific distance.
It details the process of calculating the power required for a specific task based on force, displacement, and time.
The text explores the concept of acceleration and its calculation in a scenario involving a car coming to a stop.
It outlines the calculation of force based on mass and acceleration, leading to the determination of work done.
The text concludes with the calculation of power based on work done and time, resulting in a specific power value.
It transitions to discussing collisions, explaining the conservation of linear momentum and the varying conservation of kinetic energy in different collision types.
The text categorizes collisions into elastic, inelastic, and partially inelastic, detailing the conservation of kinetic energy in elastic collisions.
It further elaborates on the conservation of momentum and kinetic energy in elastic collisions, providing equations and calculations to demonstrate the principles involved.

01:25:15

Calculating Final Velocities After Collision

The equation is written as a fraction of a s - b s, then a + b * a-b, with v2 as common.
The focus is on finding the final velocities of two masses after collision, v1 and v2.
To find v1 and v2, equations need to be solved by substituting values and converting v2 into v1.
By substituting v2 = u1 * v1 in equation one, the value of v1 is found to be m1 - m2 divided by m1 * m2 * u1.
Once v1 is known, v2 can be calculated as 2 * m1 * u1 divided by m1 + m2.
Special cases are considered, such as when both masses are equal, resulting in v1 and v2 being equal to u1.
Another scenario is explored where one mass is significantly larger than the other, causing the heavier mass to remain undisturbed while the lighter mass changes direction.
The discussion shifts to collisions in two dimensions, where x and y components of velocities are considered.
Momentum conservation is applied in two-dimensional collisions, along with the conservation of kinetic energy.

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