9
Question Question 9
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
Given,
Energy (E) = 250 units
1 kWh = 3.6 x 106 J
1 unit of energy = 1 kWh
So, 250 units of energy = 250 × 3.6 × 106 = 9 × 108 J.
Hence, 250 units of energy = 9 × 108 J.
BRIGHT TUTORIALS
BRIGHT TUTORIALS
CBSE Class IX | Academic Year 2026-2027
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Excellence in Education
Science | Chapter 10: Work and EnergyWeb Content — Quick Reference
Chapter 10: Work and Energy — Quick Reference
Quick Revision Points
- Work W = Fs cosθ (joule); W = 0 when F ⊥ s or displacement = 0
- KE = ½mv²; PE = mgh; Work-energy theorem: W = ΔKE
- Conservation: energy transforms but total remains constant; PE + KE = constant in free fall
- Power P = W/t (watt = J/s); 1 HP = 746 W
- 1 kWh = 3.6 × 10⁶ J = 1 unit of electricity
Exam Tips for Chapter 10
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
Related Resources
- Detailed Notes: ch10-work-and-energy.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html