Conservation of Mechanical Energy
Conservation of mechanical energy means that the sum of kinetic energy and potential energy remains constant when only conservative forces like gravity act and friction is neglected.
Practice This ConceptMain explanation
Teacher explanation
Mechanical energy is KE + PE. During free fall without air resistance, potential energy decreases while kinetic energy increases by the same amount. The total mechanical energy remains unchanged. With friction, some mechanical energy changes into heat and sound, so mechanical energy alone is not conserved.
Example
A freely falling ball loses gravitational potential energy and gains kinetic energy as it comes down.
Simple analogy
PE and KE trade, total stays.
Common confusion
Students often say kinetic energy remains constant during fall, but it actually increases while potential energy decreases.
Exam tip
Mention the condition clearly: mechanical energy is conserved only when friction and air resistance are ignored.
Answer writing and exam use
1-mark use
Write the exact meaning of conservation of mechanical energy in one clean line.
2-mark use
Define conservation of mechanical energy and add one example or condition.
3-mark use
Explain conservation of mechanical energy, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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