Class 9 Science — Chapter 10: Work and Energy
Chapter 10: Work and Energy is a chapter in Class 9 Science (NCERT), part of the CBSE NCERT curriculum followed by over 25 million students across India. This chapter covers 7 topics including Scientific Definition of Work, Calculating Work Done by a Constant Force, Unit of Work: The Joule. BrainWeave provides free AI-powered explanations — by voice or text, in Hindi or English — with no signup required.
What you'll learn
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▸Scientific Definition of WorkCore conceptscientific workdisplacementforceno work done
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▸Calculating Work Done by a Constant ForceCore conceptWork formulaW = Fsconstant forcecalculation
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▸Unit of Work: The JouleCore conceptjouleJSI unitnewton-metre
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▸Positive and Negative WorkCore conceptpositive worknegative workopposite directionretarding force
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▸Work Done Against GravityCore conceptgravityliftingmghvertical displacement
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▸Concept of EnergyCore conceptenergycapacity to do workwork-energypossess energy
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▸Sources of Energysources of energySunnatural sourcetides
Chapter Summary
Understand the difference between the everyday meaning of 'work' and its specific scientific definition, which requires that a force must cause a displacement in an object for work to be done.
Learn to calculate the work done by a constant force using the formula W = F × s, where the force acts in the same direction as the displacement.
Define the SI unit of work, the joule (J). Understand that 1 joule is the amount of work done when a force of 1 newton displaces an object by 1 meter along the line of action of the force.
Differentiate between positive work, where the force is in the direction of displacement, and negative work, where the force acts opposite to the direction of displacement (e.g., friction).
Calculate the work done when lifting an object against the force of gravity. This work depends on the mass of the object and the vertical height it is lifted (W = mgh).
Define energy as the capability or capacity to do work. Understand that an object possessing energy can do work, and that work done on an object results in a gain of energy for that object.
Identify various sources of energy, recognizing the Sun as the ultimate source for many others, and be aware of other sources like atomic nuclei, tides, and geothermal energy.
Practice Questions from this Chapter
Tap "Get Solution" on any question to ask our AI tutor.
- Explain work versus energy. Get Solution →
- Calculate work done moving objects. Get Solution →
- Discover energy in daily life. Get Solution →
- According to the scientific definition, which two conditions must be satisfied for work to be done on an object? Get Solution →
- What is the SI unit of work? Get Solution →
- What is the mathematical expression for work done when a constant force F acts on an object displaced by a distance s in the direction of the force? Get Solution →
- How is 1 joule (J) of work defined? Get Solution →
- Which of the following is described in the text as the biggest natural source of energy for us? Get Solution →
Did you know?
- 💡 Human brains consume about 20% of the body's total energy, even when resting.
- 💡 One lightning bolt can contain enough energy to power a house for an entire month.
- 💡 Hummingbirds must eat almost constantly because they burn energy incredibly fast.
- 💡 The Large Hadron Collider, Earth's biggest machine, uses huge energy to find tiny particles.
- 💡 You perform zero scientific work pushing a stationary wall, despite feeling exhausted.
Frequently Asked Questions
How many topics are covered in this chapter?
This chapter covers 7 key topics: Scientific Definition of Work, Calculating Work Done by a Constant Force, Unit of Work: The Joule, Positive and Negative Work, Work Done Against Gravity, and more. The BrainWeave AI tutor explains each one with examples.
Is Chapter 10: Work and Energy important for board exams?
Class 9 is a foundation year. Mastering this chapter now will help you build strong fundamentals for the higher classes.
Can I get NCERT solutions for this chapter in Hindi?
Yes. BrainWeave's AI tutor supports Hindi, English, and Hinglish for both voice and text chat. Just ask your question in your preferred language.
Is BrainWeave free for Class 9?
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