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Class 9 Physics Chapter 5: Work, Energy and Power MCQs With Explanations
Practice Class 9 Physics Chapter 5: Work, Energy and Power MCQs with explanations for Pakistani board exams. Includes solved objective questions, answer checking, chapter revision guidance and next chapter suggestions.
Chapter 5: Work, Energy and Power Objective Preparation
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50Total MCQs
46With explanations
8Topics represented
Topics found: Work Definition, Device Efficiency Comparison, Gravity Work Direction, Elastic Potential Energy, Human Power Calculation, Renewable Energy Advantages, Hydroelectric Energy Conversion, Geothermal Energy Source
Q1. The energy transferred when a force moves an object is called:
Work is defined as the transfer of energy that occurs when a force causes displacement of an object in the direction of the force.
Q2. Which of the following devices has the highest energy conversion efficiency?
Electric motors typically achieve 85–95% efficiency in converting electrical energy to mechanical energy, surpassing the efficiencies of lighting devices and internal combustion engines.
Q3. The work done by gravity on a ball thrown upward is:
Gravity acts downward while the ball moves upward, so the force and displacement are in opposite directions, resulting in negative work.
Q4. When a bow is stretched, it stores:
Stretching a bow against its restoring force stores energy as elastic potential energy, which converts to kinetic energy when released.
Q5. A 60 kg man climbs stairs of total height 5 m in 10 seconds. His power is:
Power = work/time = (mgh)/t = (60×9.8×5)/10 ≈ 294 W ≈ 300 W, using g ≈ 10 m/s² for estimation.
Q6. The main advantage of renewable energy sources is that they:
Renewable sources like solar and wind produce energy without emitting greenhouse gases or pollutants during operation.
Q7. In a hydroelectric power plant, the potential energy of water is converted to:
In a hydroelectric plant, the gravitational potential energy of stored water is converted into kinetic energy as it flows through the penstock to drive the turbine.
Q8. Which energy source uses the heat from radioactive decay inside Earth?
Geothermal energy harnesses heat generated by radioactive decay in Earth's core, making it the only option directly sourced from internal planetary heat.
Q9. The efficiency of a machine is always:
Due to energy losses from friction and heat, no real machine can be 100% efficient, so efficiency is always less than 100%.
Q10. 1 horsepower is approximately equal to:
1 mechanical horsepower is defined as approximately 746 watts.
Q11. A more powerful engine:
Power is defined as the rate at which work is done. A more powerful engine performs the same amount of work in less time, meaning it does work faster.
Q12. The energy content of food is measured in:
No explanation is available in the database for this MCQ yet.
Q13. Which energy source does not produce greenhouse gases?
Solar energy generates electricity without burning fuel, thus producing no greenhouse gases during operation.
Q14. Gravitational potential energy depends on:
Gravitational potential energy is directly proportional to an object's mass and its height above a reference point.
Q15. The kinetic energy of a body depends on:
Kinetic energy is directly proportional to mass and the square of velocity, as given by the formula KE = ½mv².
Q16. When a falling object hits the ground, its energy is converted to:
Upon impact, a falling object's kinetic energy is primarily dissipated as sound and thermal energy (heat).
Q17. A man carries a load on his head. The work done by him is:
Work is force times displacement in the direction of force; since the load is carried horizontally and gravity acts vertically, no vertical displacement occurs against gravity, so no work is done against gravity.
Q18. Which is not a unit of energy?
Watt is a unit of power (energy per time), not energy itself, while the others are units of energy.
Q19. Energy can neither be created nor destroyed, only converted from one form to another. This is the law of:
This statement is the fundamental principle of the law of conservation of energy in physics.
Q20. The energy stored in a compressed spring is:
Elastic potential energy is the energy stored in elastic materials when they are stretched or compressed, such as in a spring, due to deformation within its elastic limit.
Q21. Which device converts mechanical energy to electrical energy?
A generator uses electromagnetic induction to convert mechanical energy into electrical energy.
Q22. If a car doubles its speed, its kinetic energy becomes:
Kinetic energy is proportional to the square of speed. Doubling speed increases kinetic energy by a factor of 2² = 4.
Q23. A machine does 1000 J of work in 10 seconds. Its power is:
Power is work divided by time: 1000 J / 10 s = 100 W.
Q24. A 5 kg mass is lifted to a height of 4 m. Its gravitational potential energy is:
Potential energy = mgh = (5 kg)(10 m/s²)(4 m) = 200 J, assuming standard gravity.
Q25. If a body of mass 2 kg is moving with velocity 3 m/s, its kinetic energy is:
Kinetic energy is calculated as (1/2)mv² = (1/2)(2)(3²) = 9 J, making option B correct.
Q26. A perpetual motion machine is impossible because it violates:
Perpetual motion machines violate the law of conservation of energy by claiming to produce work indefinitely without an energy input, which is physically impossible.
Q27. The main disadvantage of fossil fuels is:
Fossil fuels release harmful pollutants like CO2, SO2, and particulates when burned, contributing to air pollution and climate change, which is their most significant environmental drawback.
Q28. Fossil fuels include:
Fossil fuels are formed from ancient organic matter and include coal, oil, and natural gas.
Q29. Nuclear energy is obtained by:
Nuclear energy is primarily generated by fission, the splitting of heavy atomic nuclei like uranium-235, releasing large amounts of energy.
Q30. The energy from ocean tides is called:
Tidal energy is specifically defined as the energy harnessed from the rise and fall of ocean tides.
Q31. Wind energy is harnessed using:
Wind turbines convert kinetic energy from wind into mechanical or electrical energy, making them the direct tool for harnessing wind energy.
Q32. Geothermal energy comes from:
Geothermal energy originates from the Earth's internal heat, primarily stored in hot rocks and magma beneath the crust.
Q33. Solar cells convert sunlight directly into:
Photovoltaic cells in solar panels convert photons from sunlight directly into electricity (electrical energy).
Q34. Hydroelectric power generation uses the energy of:
Hydroelectric power converts the energy of falling or flowing water into electrical energy using turbines and generators.
Q35. Which energy source comes from burning organic matter?
No explanation is available in the database for this MCQ yet.
Q36. Efficiency of a machine is defined as:
Efficiency is the ratio of useful output energy to input energy, expressed as a percentage. Thus, it is calculated as (Output / Input) × 100%.
Q37. A 100 W bulb consumes 100 joules of energy in:
Power is defined as energy per unit time (P = E/t), so 100 W = 100 J / 1 s.
Q38. One watt is equal to:
Watt is the SI unit of power, defined as one joule of energy transferred per second.
Q39. The SI unit of power is:
The watt is the SI unit of power, defined as one joule per second.
Q40. Power is defined as:
No explanation is available in the database for this MCQ yet.
Q41. Which of these is a renewable energy source?
Solar energy is renewable because it is derived from the sun, an inexhaustible source on human timescales.
Q42. The law of conservation of energy states that energy:
The law of conservation of energy asserts that energy cannot be created or destroyed, only transformed. In a closed system with no external inputs or outputs, the total energy remains constant over time.
Q43. The formula for gravitational potential energy is:
Gravitational potential energy is the energy an object possesses due to its height in a gravitational field, calculated as mass times gravitational acceleration times height.
Q44. The energy possessed by a body due to its position is called:
Potential energy is defined as the energy stored in an object due to its position or configuration, such as height in a gravitational field or compression in a spring.
Q45. The formula for kinetic energy is:
Kinetic energy is given by ½mv², where m is mass and v is velocity.
Q46. The energy possessed by a body due to its motion is called:
Kinetic energy is defined as the energy of motion, dependent on an object's mass and velocity.
Q47. No work is done when the angle between force and displacement is:
No explanation is available in the database for this MCQ yet.
Q48. One joule of work is done when a force of one newton displaces an object by:
One joule is defined as the work done when a force of one newton moves an object one meter in the direction of the force.
Q49. The SI unit of work is:
Joule is the SI unit of work, defined as the work done when a force of one newton displaces an object by one meter.
Q50. Work is defined as:
Work is the product of force and displacement in the direction of the force, as defined by W = F·d.
After Chapter 5: Work, Energy and Power, Practice Next Chapters
Once you finish these MCQs, continue with the next available chapters from Physics so your revision stays chapter-wise and complete.
Complete the MCQs first, then review every incorrect answer against the textbook heading where that concept appears. For biology and other science subjects, pay attention to terminology, diagrams, sequence of processes, examples and differences between similar structures or functions.
This chapter page keeps the exact class, subject, chapter, question count, answer checking, explanations and follow-up chapters together, so students can revise from one focused URL instead of searching through the full book again.
Class 9 Physics MCQ Preparation: Work, Energy and Power
This page supports Matric Part 1 practice in Physics.
At this stage, the main purpose is building the definitions, symbols, rules and study habits needed for later matric work. The questions available here should be
used with the current textbook and the instructions issued by the learner's school or examination board.
What Physics MCQs can test
In Physics, objective questions commonly draw on definitions, physical quantities, SI units, laws, graphs, diagrams, formulas and the interpretation of numerical situations.
A useful answer is based on the exact wording and concept, not simply on recognising a familiar option.
For this subject, learners should write the known quantities and units before choosing a formula, and distinguish a law from the example used to demonstrate it.
Work, Energy and Power: what to focus on
Relationships between physical quantities, direction, units, laws, graphs and the conditions under which an equation applies.
Sketch a simple situation or graph for difficult questions and check whether the selected option agrees with both the formula and the physical meaning.
Common mistakes for Class 9 learners
In this subject, frequent errors include mixing scalar and vector quantities, overlooking units, reversing cause and effect, or choosing a familiar formula without checking its conditions.
Separate new terms that look similar and connect every formula, rule or definition with at least one textbook example. When the page marks an answer as incorrect, the next step should be to identify
the mistaken idea and verify it, rather than memorising the displayed answer letter.
A practical revision routine
Read a small textbook section, answer a focused set of MCQs and correct the underlying idea before starting the next section. Before attempting the MCQs, review definitions, symbols, unit conversions, graph shapes, diagram labels and the meaning of each term in a formula.
Complete a manageable set without notes, check the result, and divide errors into missing knowledge,
misunderstood concepts and careless reading. Revise the appropriate section before repeating the chapter.
How to review Work, Energy and Power after the quiz
List the questions you missed from Work, Energy and Power and write the textbook heading
connected with each one. Explain the correct idea in your own words, then return later and answer a
fresh set. This gives the chapter page a clear purpose: finding specific weaknesses in
Physics rather than only collecting a score.
Accuracy and responsible use
Explanations are provided where they exist in the question bank, but educational databases can contain
incomplete or mistaken material. Confirm disputed answers with an authoritative textbook or teacher.
Ahmad Learning Hub provides a practice resource and does not claim that a question will appear in an
examination or that every available item represents an official board question.
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