Conservation Of Energy
Mediumphysics
A ball of mass 1 kg is dropped from a height of 20 m. What is its kinetic energy just before hitting the ground? (g = 10 m/s²)
Select the correct option:
Solution
Incorrect! Answer:
200 J
- Law of Conservation of Mechanical Energy: In the absence of friction, Etotal=K+U=constant.
- Initial State (at rest at 20 m):
- Kinitial=0.
- Uinitial=mgh=1×10×20=200 J.
- Final State (just before impact):
- Ufinal=0.
- Kfinal=Kinitial+(Uinitial−Ufinal)=0+200=200 J.
- Conclusion: All potential energy has converted into kinetic energy just before the impact.
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About This Question
- Subject
- physics
- Chapter
- work, energy and power
- Topic
- conservation of energy
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
200 J
- Law of Conservation of Mechanical Energy: In the absence of friction, Etotal=K+U=constant.
- Initial State (at rest at 20 m):
- Kinitial=0.
- Uinitial=mgh=1×10×20=200 J.
- Final State (just before impact):
- Ufinal=0.
- Kfinal=Kinitial+(Uinitial−Ufinal)=0+200=200 J.
- Conclusion: All potential energy has converted into kinetic energy just before the impact.
This medium difficulty physics question is from the chapter work, energy and power, covering the topic of conservation of energy. It appeared in the 2025 exam.
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