Work, Energy and Power

Physics, SSC-Punjab Class 9. This chapter is split into 40 topics and has 935 practice questions. The topics covered are listed below, followed by 10 free sample questions from the chapter.

Topics in this chapter

1. Power ratings of appliances 22 questions
2. Units of power: watt, kilowatt, megawatt, horse-power 26 questions
3. Exercise 5A multiple choice questions 22 questions
4. Nuclear energy 23 questions
5. Potential energy numericals 26 questions
6. Numericals on W = FS cos theta 22 questions
7. Exercise 5B short answer questions 22 questions
8. Kinetic energy: concept and derivation 24 questions
9. Energy facts and learning outcomes 24 questions
10. Hydroelectric generation 22 questions
11. Work from a force-distance graph 21 questions
12. Exercise 5D comprehensive questions 22 questions
13. Fossil fuel energy 22 questions
14. Solar energy 23 questions
15. Kinetic energy numericals 29 questions
16. Concept of work 22 questions
17. Exercise 5C constructed response questions 23 questions
18. Perpetual energy machines 21 questions
19. Numericals on W = F x S 24 questions
20. Potential energy and its forms 23 questions
21. Power: concept and definition 22 questions
22. Tidal and wave energy 24 questions
23. Work done at an angle W = FS cos theta 23 questions
24. Biofuel energy 23 questions
25. Renewable and non-renewable sources 24 questions
26. Power station stages and block diagrams 23 questions
27. Advantages and disadvantages of energy production 23 questions
28. Efficiency numericals 26 questions
29. Units of work: the joule 23 questions
30. Key points of Chapter 5 25 questions
31. Efficiency: concept and examples 23 questions
32. Economic social and environmental impact of energy sources 22 questions
33. Exercise 5E numerical problems 25 questions
34. Energy conversions in daily life 22 questions
35. Law of conservation of energy 24 questions
36. Power numericals 28 questions
37. Wind energy 21 questions
38. Geothermal energy 21 questions
39. Conservation of energy numericals 27 questions
40. Energy and its forms 23 questions

Sample questions: Work, Energy and Power

10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.

Q1. A person carries a suitcase up a staircase of vertical height h. Compared with carrying it along level ground for the same horizontal distance, in physics terms the person:

• A. does work against gravity on the suitcase going upstairs, but none against gravity on level ground(correct answer)
• B. does the same work against gravity in both cases
• C. does work only when standing still
• D. does no work on the suitcase in either case

Answer: A.Lifting the suitcase through a height has an upward force along an upward displacement; on level ground the supporting force is perpendicular to the displacement.

Q2. Which learning outcome statement lists the ways energy may be STORED?

• A. Pressure, density, volume and temperature
• B. Work, power, efficiency and pressure
• C. Gravitational potential, chemical, elastic (strain), nuclear, electrostatic and internal (thermal) energies(correct answer)
• D. Force, mass, velocity and acceleration

Answer: C.The chapter's learning outcomes say energy may be stored as gravitational potential, chemical, elastic, nuclear, electrostatic and internal energies.

Q3. The 'For Your Information' box on p. 111 says that, according to Einstein's theory of relativity:

From your book: see this page (page 111) Full page Open book

From your book: see this page (page 112) Full page Open book

• A. matter and energy are interchangeable under certain conditions(correct answer)
• B. energy is always conserved separately from matter
• C. mass cannot change
• D. energy is a vector

Answer: A.The loss of some mass in nuclear reactions produces energy, so we now speak of conservation of mass and energy rather than of each separately.

Q4. A man rowing a boat upstream is at rest with respect to the shore. Is he doing work (on the shore frame)?

• A. No, because there is no energy
• B. Yes, because he is moving the oars
• C. No, the boat is not displaced relative to the shore, so no work is done by him on the boat in that frame(correct answer)
• D. Yes, because there is a force

Answer: C.Work requires displacement; with no displacement relative to the shore there is no work in that frame (Constructed Response 5.7). He still spends chemical energy.

Q5. The Student Learning Outcomes list hydroelectric resources among natural resources from which useful energy may be obtained, together with:

• A. only nuclear fuel
• B. fossil fuels, biofuels, solar radiation, nuclear fuel, geothermal, wind, tides and sea waves(correct answer)
• C. only fossil fuels
• D. only solar energy

Answer: B.The outcome lists (a)-(i) including chemical energy in fossil fuels and biofuels, hydroelectric, solar, nuclear, geothermal, wind, tides and waves.

Q6. Which sequence describes a geothermal power plant?

• A. Cold water pumped down → heated by hot rocks into steam → steam turns turbine → generator makes electricity(correct answer)
• B. Steam turns turbine → water pumped down → rocks burn → generator cools
• C. Hot rocks burn → water falls → turbine cools → steam is produced
• D. Generator makes steam → turbine heats rocks

Answer: A.See Fig. 5.17 of the book. The correct answer is: Cold water pumped down → heated by hot rocks into steam → steam turns turbine → generator makes electricity.

Q7. Compare an advantage of hydroelectric power with one of nuclear power given in the book.

• A. Both produce smoke
• B. Hydroelectric is the cheapest and pollution free; nuclear is described as cheaper and able to meet increasing demand easily(correct answer)
• C. Both are free of any danger
• D. Both use fossil fuels

Answer: B.The Impact box states these. The correct answer is: Hydroelectric is the cheapest and pollution free; nuclear is described as cheaper and able to meet increasing demand easily.

Q8. Compare an ideal machine and a perpetual machine.

• A. An ideal machine has output equal to input (100%); a perpetual machine would produce work without any input; neither can be built(correct answer)
• B. A perpetual machine has 50% efficiency
• C. Both are real machines
• D. An ideal machine produces more than the input

Answer: A.Both are hypothetical per the book. The correct answer is: An ideal machine has output equal to input (100%); a perpetual machine would produce work without any input; neither can be built.

Q9. Short Answer 5.10: Which statement differentiates renewable from non-renewable sources?

• A. Renewable sources are polluting, while non-renewable are not
• B. Renewable sources are burnt, non-renewable are not
• C. There is no difference
• D. Renewable sources are replaced by new ones after use, while non-renewable sources are not easily replaced(correct answer)

Answer: D.Definition from section 5.5. The correct answer is: Renewable sources are replaced by new ones after use, while non-renewable sources are not easily replaced.

Q10. Comprehensive Question 5.2 asks to state the law of conservation of energy. The correct statement is:

From your book: see this page (page 112) Full page Open book

From your book: see this page (page 113) Full page Open book

• A. Energy can be created
• B. Energy always increases
• C. Energy cannot be created or destroyed; it may be transformed from one form to another, but the total amount never changes(correct answer)
• D. Energy is destroyed in friction

Answer: C.Section 5.3. The correct answer is: Energy cannot be created or destroyed; it may be transformed from one form to another, but the total amount never changes.