Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Mechanics ↓


Work, Energy and Power


Introduction

In physics, understanding the concepts of work, energy, and power is important to understand how objects move and interact in the world around us. These concepts are not only essential for physics but also apply in various fields such as engineering, biology, and chemistry. Let us explore these concepts in detail.

What is the work?

In the context of physics, work is defined as when a force causes an object to move in the direction of the force. Work is only done when there is motion, and it is calculated using the formula:

Work (W) = Force (F) × Distance (d) × cos(θ)

Where:

  • W is the work done, measured in joules (J).
  • F is the applied force in Newtons (N).
  • d is the distance traveled in meters.
  • θ is the angle between the force and the direction of motion.

For example, if you push a box 2 meters with a force of 10 N, the work done is:

W = 10 N × 2 m × cos(0°) = 20 J

Understanding energy

Energy is the capacity to do work. It exists in various forms, such as mechanical, thermal, chemical and nuclear energy. In mechanics, we focus mainly on mechanical energy, which is of two main types: kinetic and potential energy.

Kinetic energy

Kinetic energy is the energy of motion. Any moving object has kinetic energy, which can be calculated using the formula:

Kinetic Energy (KE) = 0.5 × mass (m) × velocity (v)²

Where:

  • m is the mass of the object in kilograms (kg).
  • v is the velocity of the object in meters per second (m/s).

Potential energy

Potential energy is energy stored because of an object's position or state. A common type is gravitational potential energy, which is determined by an object's height and mass relative to the Earth's gravitational pull. The formula is:

Potential Energy (PE) = mass (m) × gravitational acceleration (g) × height (h)

Where:

  • g is the gravitational acceleration (about 9.8 m/s² on Earth).

For example, a rock at the top of a cliff has potential energy that can be converted into kinetic energy as it falls.

Illustration of energy conversion

Below is a visual example of energy conversion:

potential energy kinetic energy

Discovery of power

Power is the rate of doing work or converting energy. It determines how fast work is done or how fast energy is converted. The unit of power is the watt (W), named after James Watt, who played a key role in the development of the steam engine. Power is calculated using the formula:

Power (P) = Work done (W) / Time taken (t)

If a person lifts a box of 50 Newton force to a height of 2 m in 5 seconds, then the work done will be:
W = 50 N × 2 m = 100 J

Therefore, the power is:

P = 100 J / 5 s = 20 W

This means that the person expended 20 watts of power during the lift.

Relation between work, energy and power

Work and energy are closely related; work done on an object results in a change in its energy. When work is done on an object, its energy either increases or decreases. Power, on the other hand, measures how quickly this work or energy transfer is taking place.

Consider a car engine:

  • Function: The engine works to move the car.
  • Energy: Chemical energy from the fuel is converted into mechanical energy.
  • Power: This tells how quickly the engine can do work.

Example Problems

Problem 1: Calculating Work

A person pushes a shopping cart a distance of 10 m with a force of 30 N. Calculate the work done.

Solution:

W = F × d = 30 N × 10 m = 300 J

The work done is 300 joules.

Problem 2: Kinetic Energy Calculation

A car of mass 1500 kg is moving at a velocity of 20 m/s. Calculate its kinetic energy.

Solution:

KE = 0.5 × m × v² = 0.5 × 1500 kg × (20 m/s)² = 300000 J

The kinetic energy of the car is 300,000 joules.

Problem 3: Power in action

A light bulb uses 60 joules of energy in 3 seconds. Calculate the power consumed by the light bulb.

Solution:

P = E / t = 60 J / 3 s = 20 W

The power consumed by the light bulb is 20 watts.

Conclusion

In short, work, energy, and power are fundamental concepts in mechanics that describe the motion and interaction of objects. Understanding these concepts helps us understand how physical forces affect the world around us.

The study of work, energy, and power helps us solve practical problems, such as calculating the energy efficiency of a machine or understanding how different forms of energy are transferred and converted.


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