Ch 6 covers the scalar product definition of work, the work-energy theorem, potential energy, conservative forces, conservation of mechanical energy, different types of collisions, and power.
Work by constant force: W = F·d cosθ. By variable force: W = ∫F·dx (area under F-x graph). Work-energy theorem: net work done on a body = change in its kinetic energy (W_net = ½mv² − ½mu²). This is a powerful problem-solving tool.
Conservative forces (gravity, spring): work depends only on initial and final positions, not path. PE associated with position: gravitational PE = mgh, spring PE = ½kx². Conservation of energy: E_total = KE + PE = constant (when only conservative forces act).
Elastic collision: both KE and momentum conserved (e.g., billiard balls). Inelastic collision: momentum conserved but KE is not (some converted to heat, sound). Perfectly inelastic: objects stick together (max KE loss). In 1D elastic collision: v₁ = ((m₁−m₂)u₁ + 2m₂u₂)/(m₁+m₂).
Download: https://ncert.nic.in/textbook/pdf/keph106.pdf | Part I: https://ncert.nic.in/textbook/pdf/keph1ps.zip
In an elastic collision, both kinetic energy and momentum are conserved — objects bounce apart with no energy loss (ideal billiard balls). In an inelastic collision, momentum is conserved but kinetic energy is not — some energy converts to heat, sound, or deformation. In a perfectly inelastic collision, objects stick together (e.g., a bullet embedding in a block).
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