Page 1: Introduction
Work and energy are interrelated concepts used to explain motion and forces.
Work is done when force causes displacement.
Energy is the capacity to do work.
Law of conservation of energy is fundamental.
Page 2: Work Done by a Force
(F = force, s = displacement, θ = angle between F and s)
Unit: Joule (J) = 1 N·m
Page 3: Cases of Work
- Positive work: θ < 90° (force in direction of displacement)
- Zero work: θ = 90° (perpendicular, e.g., carrying load horizontally)
- Negative work: θ > 90° (opposing displacement)
Page 4: Energy
Capacity to do work.
Unit: Joule (same as work)
Forms: kinetic, potential, mechanical, etc.
Page 5: Kinetic Energy
(m = mass, v = velocity)
Derived from work-energy theorem.
Page 6: Potential Energy
(h = height above reference)
Stored due to position.
Page 7: Law of Conservation of Energy
Total energy remains constant.
Energy transforms from one form to another.
Example: free fall — PE → KE
Page 8: Power
Unit: Watt (W) = 1 J/s
Commercial unit: kWh
1 kWh = 3.6 × 10⁶ J
Page 9: Work-Energy Theorem
Work done by net force = change in kinetic energy
W_net = ΔKE = (1/2)mv² - (1/2)mu²
Page 10: Key Formulas Summary
- W = Fs cosθ
- KE = (1/2)mv²
- PE = mgh
- P = W/t
- 1 kWh = 3.6 MJ
Page 11: Practice Questions - Easy (1-10)
- Unit of work.
- KE formula.
- When work zero?
- Power unit.
- Conservation of energy statement.
- PE at ground level.
- 1 kWh in joules.
- Work by gravity in lifting.
- KE of stationary object.
- Power = ?
Page 12: Practice Questions - Medium (11-20)
- Work done lifting 10 kg by 5 m (g=10).
- KE of 2 kg at 5 m/s.
- Power of person doing 500 J in 10 s.
- Velocity for KE 200 J, m=4 kg.
- Height for PE 1000 J, m=20 kg.
- Work against gravity numerical.
- Free fall: total energy constant.
- Power in kW for 3600000 J in 1 hour.
- Work by constant force perpendicular.
- Change in KE numerical.
Page 13: Practice Questions - Hard (21-30)
- Object thrown up: max height, energy conversion.
- Power of pump lifting water.
- Work-energy theorem application.
- Conservation in pendulum.
- Force from power and velocity.
- Combined KE + PE problem.
- Electrical unit conversion.
- Roller coaster energy.
- Negative work example numerical.
- Advanced power calculation.
Page 14: NCERT Exercise Types
Numerical on work, KE, PE, power, conservation.
Page 15: Common Mistakes
- Forgetting cosθ in work
- Wrong sign in negative work
- Confusing KE and PE
- Unit conversion error in power
- Not taking g=10 when given
Page 16: Previous Year Questions
Work calculation, power, conservation, KE-PE conversion.
Page 17: Exam Tips
- Write formula first
- Show substitution
- Use g value as per question
- Explain conservation clearly
- Units mandatory
Page 18: Quick Revision Sheet
All formulas, units, cases.
Page 19: Real-Life Applications
Hydroelectric power, vehicles, sports.
Page 20: Final Motivation
Chapter 11 complete! Work and Energy is highly scoring.
Practice numericals and conservation problems.
Board Buddy Physics almost done 🦖
Page 21: Extra Numericals
More solved problems.
Page 22: Conservation Examples
Pendulum, free fall, roller coaster.
Page 23: Power Calculations
Steps and examples.
Page 24: Work Cases Table
Positive, negative, zero with examples.
Page 25: Energy Transformation
Common conversions.
Page 26: Formula Table
All important equations.
Page 27: Thank You & Copyright
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