Kinetic Energy Theorem and Conservation of Mechanical Energy
This page delves into the théorème de l'énergie cinétique and the concept of conservation of mechanical energy.
Definition: The théorème de l'énergie cinétique states that the change in kinetic energy of a system moving along a displacement AB is equal to the sum of the work done by external forces applied during the motion.
The theorem is expressed mathematically as:
ΔE = Ec₁ - Ec₂ = WFext
Where:
- ΔE is the change in kinetic energy
- Ec₁ and Ec₂ are initial and final kinetic energies
- WFext is the work done by external forces
The page then introduces the concept of mechanical energy conservation:
Highlight: Mechanical energy Em is the sum of kinetic energy Ec and potential energy Epp.
Em = Ec + Epp
For gravitational potential energy: Epp = mgz, where m is mass, g is gravitational acceleration, and z is altitude in meters.
Definition: A conservative force is one whose work during a displacement from A to B does not depend on the path chosen.
The page concludes with two important principles:
- For systems with only conservative forces: ΔEmA→B = 0
- For systems with non-conservative forces: ΔEmA→B = WFnc
Vocabulary:
- Conservative force: A force whose work is path-independent e.g.,gravity
- Non-conservative force: A force whose work depends on the path taken e.g.,friction
These concepts are crucial for understanding energy transformations in mechanical systems and form the basis for solving complex problems in physics.