Ch 11 defines work scientifically (force × displacement), introduces kinetic and potential energy, derives the work-energy theorem, and covers the law of conservation of energy and power.
Work is done when a force displaces an object: W = F × s (when F and s are in the same direction). W = Fs cos θ (when angle θ between force and displacement). No work if: no displacement, force perpendicular to displacement. SI unit: joule (1 J = 1 N × 1 m).
Energy: capacity to do work. Kinetic energy (energy of motion) = ½mv². Potential energy (energy of position) = mgh (gravitational PE). Work-energy theorem: work done = change in KE. Law of conservation of energy: energy can neither be created nor destroyed, only transformed.
Power = rate of doing work = work/time. SI unit: watt (1 W = 1 J/s). 1 horsepower (hp) = 746 W. Commercial unit: kilowatt-hour (kWh). 1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J. This is the "unit" on electricity bills.
Download: https://ncert.nic.in/textbook/pdf/iesc111.pdf | Complete book: https://ncert.nic.in/textbook/pdf/iesc1ps.zip
No, scientifically no work is done because there is no displacement. Even though you feel tired (muscles contract and expand internally, doing biological work), the bag does not move, so W = F × 0 = 0.
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