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HSSLIVE Plus One Physics Chapter 6: Work, Energy and Power Notes

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Work, Energy and Power introduces students to energy concepts that revolutionize problem-solving beyond force-based approaches. This chapter connects the concepts of work done by forces to changes in kinetic and potential energies, leading to the powerful principle of conservation of energy. Students learn to calculate power and efficiency while applying energy conservation to analyze complex mechanical systems, from simple machines to roller coasters.

Plus One Physics Notes – Chapter 6: Work, Energy and Power

SCERT Kerala Board

Work

Definition: Work is done when a force causes displacement of an object in the direction of the force.

Mathematical expression: W = F·d·cosθ

  • W = work done (joules, J)
  • F = force applied (newtons, N)
  • d = displacement (meters, m)
  • θ = angle between force and displacement vectors

Key points:

  • Work is a scalar quantity (has magnitude but no direction)
  • Work can be positive, negative, or zero
  • Zero work occurs when force and displacement are perpendicular (θ = 90°)
  • Negative work occurs when force opposes displacement (90° < θ ≤ 180°)

Energy

Definition: Energy is the capacity to do work.

Types of Energy:

  1. Kinetic Energy (KE): Energy possessed by an object due to its motion
    • KE = ½mv²
    • m = mass (kg)
    • v = velocity (m/s)
  2. Potential Energy (PE): Energy possessed by an object due to its position or configuration
    • Gravitational PE: PE = mgh
      • m = mass (kg)
      • g = acceleration due to gravity (9.8 m/s²)
      • h = height (m)
    • Elastic PE: PE = ½kx²
      • k = spring constant (N/m)
      • x = extension or compression (m)

Conservation of Energy: Energy can neither be created nor destroyed; it can only be transformed from one form to another.

Power

Definition: Power is the rate at which work is done or energy is transferred.

Mathematical expression:

  • P = W/t
  • P = F·v (when force is constant and in direction of motion)

Where:

  • P = power (watts, W)
  • W = work done (joules, J)
  • t = time taken (seconds, s)
  • F = force (newtons, N)
  • v = velocity (m/s)

Units:

  • 1 watt (W) = 1 joule/second (J/s)
  • 1 kilowatt (kW) = 1000 W
  • 1 horsepower (hp) = 746 W

Work-Energy Theorem

The work done by all forces acting on an object equals the change in kinetic energy of the object.

W = ΔKE = KEfinal – KEinitial

Collisions and Conservation Laws

  1. Elastic collision: Both momentum and kinetic energy are conserved
  2. Inelastic collision: Only momentum is conserved, kinetic energy is not conserved
  3. Perfectly inelastic collision: Objects stick together after collision

Practice Problems

  1. Calculate the work done when a force of 20 N moves an object 5 m at an angle of 30° to the horizontal.
  2. A 2 kg object is lifted 10 m above the ground. Calculate its potential energy.
  3. Find the power developed by an engine that does 20,000 J of work in 10 seconds.

Key Formulas to Remember

  • Work: W = F·d·cosθ
  • Kinetic Energy: KE = ½mv²
  • Gravitational Potential Energy: PE = mgh
  • Elastic Potential Energy: PE = ½kx²
  • Power: P = W/t or P = F·v
  • Work-Energy Theorem: W = ΔKE

These notes cover the essential concepts of Work, Energy and Power for Plus One Physics following the SCERT Kerala Board syllabus. The material is presented in a simplified manner to aid understanding and retention.

Complete Chapter-wise Hsslive Plus One Physics Notes

Our Hsslive Plus One physics notes cover all chapters with key focus areas to help you organize your study effectively:

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