Grade 11
  1. Mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two and three dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration and deceleration  1.1.6. Graphical analysis of motion  1.1.7. Equations of motion (advanced derivations)  1.1.8. Free fall and terminal velocity  1.1.9. Projectile motion  1.1.10. Relative velocity in one and two dimensions  1.1.11. Motion of a car on an inclined plane  1.2. Dynamics  1.2.1. Newton's laws of motion and their applications  1.2.2. Inertia and Newton's first law  1.2.3. Force and types of force  1.2.4. Static and kinetic friction  1.2.5. Circular motion and centripetal acceleration  1.2.6. Non-uniform circular motion  1.2.7. Banking of roads and curves  1.2.8. Momentum and Impulse  1.2.9. Conservation of momentum in one and two dimensions  1.2.10. Applications of Newton's Third Law  1.3. Work, Energy and Power  1.3.1. Work done by a constant and variable force  1.3.2. Work–energy theorem  1.3.3. Kinetic and potential energy  1.3.4. Gravitational and elastic potential energy  1.3.5. Conservation of mechanical energy  1.3.6. Power and instantaneous power  1.3.7. Efficiency of machines  1.3.8. Work done by conservative and non-conservative forces  1.4. Rotational motion  1.4.1. Torque and angular acceleration  1.4.2. Rotational equilibrium  1.4.3. Moment of inertia and its applications  1.4.4. Angular momentum and its conservation  1.4.5. Kinetic energy of rolling motion and rotation  1.4.6. Parallel and Perpendicular Axis Theorem  1.4.7. Dynamics of rotational motion
  2. Gravitational force  2.1. Universal gravitation  2.1.1. Newton's law of universal gravitation  2.1.2. Gravitational field and potential  2.1.3. Change in acceleration due to gravity  2.1.4. Kepler's laws of planetary motion  2.1.5. Orbital mechanics and satellites  2.1.6. Escape velocity and orbital velocity  2.1.7. Weightlessness and free fall  2.1.8. Gravitational potential energy and energy in orbits  2.1.9. Black holes and gravitational lensing
  3. Properties of matter  3.1. Fluid mechanics  3.1.1. Density and pressure in liquids  3.1.2. Pascal's theory and applications  3.1.3. Archimedes' Principle and Buoyancy  3.1.4. Bernoulli's equation and applications  3.1.5. Continuity equation and the Venturi effect  3.1.6. Surface tension and capillarity  3.1.7. Viscosity and Poiseuille's Law  3.1.8. Reynolds number and turbulence  3.2. Elasticity and deformation  3.2.1. Hooke's law and the stress-strain relation  3.2.2. Elastic modulus and applications  3.2.3. Deformation and yield strength of solids
  4. Thermal physics  4.1. Heat and temperature  4.1.1. Thermometric properties and temperature scale  4.1.2. Thermal expansion of solids, liquids and gases  4.1.3. Heat transfer system  4.1.4. Specific heat capacity and calorimetry  4.1.5. Latent heat and phase change  4.2. Kinetic theory of gases  4.2.1. Molecular model of gases  4.2.2. Kinetic explanation of temperature  4.2.3. Ideal Gas Equation and Deviations  4.2.4. Mean free path and Maxwell–Boltzmann distribution  4.3. Laws of Thermodynamics  4.3.1. Zeroth Law and Thermal Equilibrium  4.3.2. First Law and Internal Energy  4.3.3. The Second Law and Entropy  4.3.4. Carnot cycle and heat engines  4.3.5. Refrigerators and heat pumps
  5. Waves and oscillations  5.1. Simple Harmonic Motion  5.1.1. Equations of SHM  5.1.2. Energy in SHM  5.1.3. Damped and forced oscillations  5.1.4. Resonance and applications  5.1.5. Pendulum and spring-mass system  5.2. Wave motion  5.2.1. Types of mechanical waves  5.2.2. Wave motion and energy transport  5.2.3. Superposition Principle and Standing Waves  5.2.4. Reflection, Refraction and Diffraction  5.2.5. Doppler effect in sound and light  5.2.6. Pulsations and interference
  6. Electricity and Magnetism  6.1. Electrostatics  6.1.1. Electric charge and conservation  6.1.2. Coulomb's law and its applications  6.1.3. Electric field and electric flux  6.1.4. Electric potential and potential energy  6.1.5. Capacitance and Energy Stored in a Capacitor  6.2. Current Electricity  6.2.1. Ohm's law and electrical resistance  6.2.2. Resistivity and temperature dependence  6.2.3. Kirchhoff's Laws and Circuit Analysis  6.2.4. Electrical power and efficiency  6.2.5. Combination of resistors  6.3. Magnetism and Electromagnetism  6.3.1. Magnetic fields and their sources  6.3.2. Magnetic force on moving charges  6.3.3. Electromagnetic induction  6.3.4. Faraday's and Lenz's laws  6.3.5. Inductance and Transformer  6.3.6. Alternating current and its applications
  7. Optics  7.1. Reflection and Refraction  7.1.1. laws of reflection and refraction  7.1.2. Mirrors and lenses  7.1.3. Total internal reflection and optical fiber  7.2. Wave optics  7.2.1. Interference and Diffraction  7.2.2. Young's double-slit experiment  7.2.3. Polarization of light
  8. Modern Physics  8.1.1. Photoelectric effect and Einstein's theory  8.1.2. Wave–particle duality  8.1.3. Heisenberg's uncertainty principle  8.1.4. Compton Effect  8.2. Atomic and Nuclear Physics  8.2.1. Atomic model and energy levels  8.2.2. Radioactive decay and half-life  8.2.3. Nuclear Fission and Fusion
  9. Electronics and Communication  9.1. Semiconductors  9.1.1. pn junction and diode  9.1.2. Transistors and Logic Gates  9.1.3. Integrated Circuits and Applications  9.2. Communication Systems  9.2.1. Basics of Analog and Digital Communication  9.2.2. Wireless and Optical Communication  9.2.3. Modulation and Demodulation

Grade 11 → Mechanics ↓


Work, Energy and Power


In the study of mechanics under physics, the concepts of work, energy and power are essential to understand the various motions and behaviours of objects. Let us look at these concepts one by one with detailed explanations and examples, both theoretically and visually.

Work

Work is a measure of energy transfer that occurs when an object is moved a distance by an external force, usually aligned with the direction of displacement. The formal definition is based on mathematical terms where work is the product of the applied force and the distance moved in the direction of the force.

The formula for calculating work is expressed as:

W = F × d × cos(θ)

Where:

  • W is the work done (in joules, J)
  • F is the force applied (in newtons, N)
  • d is the displacement (in meters, m)
  • θ is the angle between the direction of force and displacement.

Example of work

Imagine you are pushing a box on the floor. If you apply a force of 10 N to move the box 5 m on the floor in the direction of your push, while the direction of your force is the same as the direction of motion:

Use of the formula:

W = 10 × 5 × cos(0) = 50 J

The work done is 50 J because cos(0) = 1.

Force

Energy

Energy is the capacity to do work. It exists in many forms such as kinetic energy, potential energy, thermal energy, and others. In mechanics, we often deal with kinetic and potential energy.

Kinetic energy

Kinetic energy is the energy that an object has due to its motion. It is given by the formula:

KE = 0.5 × m × v²

Where:

  • KE is kinetic energy (in joules, J)
  • m is the mass of the object (in kilograms)
  • v is the velocity of the object (in meters per second, m/s)

Example of kinetic energy

A car with a mass of 1000 kg is moving at a speed of 20 m/s. Its kinetic energy can be calculated as:

KE = 0.5 × 1000 × (20)² = 200,000 J

The car has 200,000 joules of kinetic energy.

Potential energy

Potential energy is the stored energy that an object possesses because of its position or state. The most common form of potential energy in mechanics is gravitational potential energy, which depends on the height of an object above some reference point.

The formula for gravitational potential energy is:

PE = m × g × h

Where:

  • PE is the potential energy (in joules, J)
  • m is the mass (in kilograms)
  • g is the acceleration due to gravity (9.8 m/s² on Earth)
  • h is the height (in meters, m)

Example of potential energy

Suppose a book with a mass of 1.5 kg is placed on a shelf at a height of 2 m. The gravitational potential energy relative to the floor can be found using the formula:

PE = 1.5 × 9.8 × 2 = 29.4 J

The potential energy of the book is 29.4 joules.

Power

Power is the rate at which work is done or energy is transferred. It tells us how quickly work is being done or energy is being used, and it is measured in watts (W) where one watt is equal to one joule per second.

The formula to calculate power is:

P = W / t

Where:

  • P is the power (in watts, W)
  • W is the work done (in joules, J)
  • t is the time taken (in seconds)

Example of power

If a light bulb uses 120 joules of energy in 60 seconds, then the power consumed by the light bulb is:

P = 120 / 60 = 2 W

The light bulb uses electricity at the rate of 2 watts.

Bulb

Relation between work, energy and power

In mechanics, the concepts of work, energy, and power are interconnected. When work is done on an object, energy is transferred, which can change the object's kinetic or potential energy. Power determines how quickly this transfer of energy occurs.

Consider a scenario where you lift a box. The work done on the box changes its potential energy, as it gains height. The energy required to lift it yields power, which depends on how fast you lift the box.

Raise

Conclusion

Understanding work, energy, and power provides an important framework for analyzing physical phenomena. Work is the action of applying force to move an object, which can result in a change in energy. Kinetic and potential energy are the two main types, representing the speed and position of an object, respectively. Power measures how quickly work can be done or energy can be used.

In daily life, these concepts help explain how machines work, how energy is consumed, or how force and motion result in meaningful actions. By mastering these fundamentals, students can better understand mechanics as part of their physics education.


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Work, Energy and Power

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