Question Answer
Work and Energy Question Answer Practice
Work and Energy question answer practice for Class 9 Science revision.
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FAQ
Why do we feel tired even if no work is done in physics terms?
We feel tired because our body uses energy to apply force or maintain a position, even if there is no displacement. You can listen to the full explanation on Harshali Academy.
How is power related to work?
Power is the rate at which work is done, meaning how fast work is completed. Harshali Academy explains this concept with simple examples.
Can work be done if force and displacement are perpendicular?
No, because work depends on the component of force in the direction of displacement. If force is perpendicular, work done is zero. Harshali Academy covers this important point clearly.
What is the SI unit of work and how is one joule defined?
The SI unit of work is joule. One joule is done when a force of one newton moves an object by one meter in the direction of the force.
How does energy relate to work done on an object?
When work is done on an object, energy is transferred to it. Energy is the capacity to do work, so work transfers energy from one form to another.
Important exam questions with answers
Define work in physics and state the conditions required for work to be done.
Work is said to be done when a force is applied on an object and the object moves in the direction of the force. Both force and displacement in the direction of force must be present for work to be done.
Is work done when you hold a heavy bag stationary on your head? Explain.
No work is done because although force is applied to hold the bag, there is no displacement of the bag. Work requires displacement in the direction of force.
What is the difference between kinetic energy and potential energy?
Potential energy is the stored energy of an object due to its position or height. Kinetic energy is the energy an object has due to its motion after work is done on it.
Key concepts from this chapter
- Work in physics requires both force and displacement in the direction of force.
- No work is done if there is no displacement, even if force is applied.
- Work done is calculated as Work = Force × Displacement × cosθ, where θ is the angle between force and displacement.
- Energy is the capacity to do work; it can be potential or kinetic.
- Potential energy is stored energy due to position; kinetic energy is energy of motion when an object moves after work is done on it by a force applied in its direction of displacement. Power is the rate at which work is done.
Question-answer focus
Imagine waking up early in the morning, getting ready for school, carrying your bag, and walking to the bus stop. You feel tired by the end of the day and say, “I have done so much work today.” But in Class 9 Science Chapter 10 Work and Energy, we learn that not all efforts count as work in physics. This chapter explains the true meaning of work, energy, and power through examples like pushing a heavy rock or climbing stairs with a bag. Harshali Academy’s clear explanations help students understand these concepts deeply. Listening to the full chapter on Harshali Academy will make these scientific ideas easy and memorable. This question-answer page helps students practise likely doubts and exam responses from Work and Energy before downloading the full app.
Hindi explanation
कल्पना करें कि सुबह का समय है और आप स्कूल जाने के लिए तैयार हो रहे हैं। आप अपना बैग उठाते हैं और बस स्टॉप तक चलते हैं। दिन भर की थकान के बाद आप कहते हैं कि आपने बहुत काम किया। लेकिन कक्षा 9वीं विज्ञान अध्याय 10 कार्य और ऊर्जा में हम सीखते हैं कि भौतिकी में कार्य का मतलब क्या होता है। यह अध्याय कार्य, ऊर्जा और शक्ति के बारे में सरल उदाहरणों से समझाता है।
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