NCERT Solutions for Class 9 Science Chapter 11
Important NCERT Questions
Work and Energy
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-158
Questions No-6
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
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1. Law of Conservation of Energy:
– The law states that in a closed system, the total energy remains constant over time; energy can neither be created nor destroyed, only transformed from one form to another.
2. Initial Potential Energy:
– Initially, a freely falling object possesses potential energy due to its position above a reference level (PE = mgh, where m is mass, g is acceleration due to gravity, and h is height).
3. Progressive Decrease in Potential Energy:
– As the object falls, its height decreases, leading to a reduction in its potential energy.
– The decrease in height results in a corresponding decrease in potential energy.
4. Compensation by Kinetic Energy:
– Simultaneously, as the object falls, its velocity increases due to gravitational acceleration.
– The increase in velocity corresponds to an increase in kinetic energy (KE = 0.5 m x v², where v is velocity).
5. Energy Transformation:
– The decrease in potential energy is precisely balanced by the increase in kinetic energy.
– The total energy, which includes potential and kinetic energies, remains constant throughout the fall.
6. Conservation of Total Energy:
– The sum of the object’s kinetic and potential energies remains constant as it falls.
– This transformation of energy from potential to kinetic showcases the conservation of total energy within the system.
Understanding this process emphasizes the conversion of potential energy into kinetic energy during the fall of an object, while the total energy within the system remains constant, thereby complying with the law of conservation of energy.